This post was taken from TwinTurbo.Net. I did not link to the article because too many times I have linked to good data only to have it unavailable at a later tine. All credit is given to Russell Floyd as noted who originally posted this

NA & TT differences and Conversion hints. Russell Floyd ZX Connection (Exclusively Z32) Used parts, service, performance, sales. zxparts@mindspring.com 770-562-8668 I have gathered all this info over the past couple years. I have tons of TT and NA parts to look at and a Nissan Computer system at my disposal, so you can bet that this info is accurate. I get tons of emails/calls asking if we can do a conversion or can sell the parts to do it. So this is my response below. We can do it for around $6,000 if you have a 5 sp NA, around a $1000 more if you have an auto, because we have to change the transmissions then. We can also convert 5p to auto and vice versa for extra cost. These prices are ballpark and depend on the situation. They are with exchange of good NA parts and involve converting to a stock TT with used parts. We do recommend installing certain parts new and upgrading certain things while we have everything apart for minimal extra labor costs. But that just depends on how far you want to go, it is easy to get up to $10-$15k quickly if you want a lot of performance parts. It is more practical to sell the NA and buy a TT in most situations but there are exceptions that we understand. The only way we see fit to do the conversion is to buy a wrecked TT (which we have quite a few of) and transfer everything into the NA being converted, buying stuff piece by piece will take forever and become very expensive. The majority of the differences are listed below, if you have any disagreement with what I have listed I would like to know, feel free to call. We are working towards becoming THE source for anything Z32 related and the 350Z soon enough. We have a former Nissan parts manager (20 years) Larry Blackwell and a team of mechanics (Reuben and Shawn) and sales people (Robert and John) that are determined to be #1 in anything Nissan Z related in the next few years. ENGINE 1. The blocks are the same. They both have oil squirters that direct oil towards the underside of the piston, but they point at different angles. The oil squirters on the TT direct oil straight into a off center hole on the underside of the TT piston, which leads to a hollow area inside the top of the TT piston. The NA ones just direct the oil towards the middle of the underside of the piston which has no passages inside. They blocks have all of the same oil passages. Two passages are plugged with a bolt on the NA block (one on each outside face that feed the turbos on a TT). The TT has two oil passages plugged inside where the oil filter bracket mounts, the NA has two small check valves in this location. They are plugged in the TT providing more pressure so that the oil will go through the lines to the oil cooler, which returns back to the oil pan. There are check valves on the inside of the TT oil filter bracket where the oil filter screws on, but none on the NA The purpose of these check valves is if the oil filter somehow becomes clogged or collapses that oil will still circulate. 2. The crankshaft is the same. 3. Connecting rods ARE the same!! (Same Nissan part #) 4. Piston rings, and Crankshaft (main) bearings are the same. The rod bearings are the same size but the TT ones are a different alloy (kelmet). 5. Of course the pistons are different because of lower compression ratio in the TT, 8.5:1 in respect to 10.5:1 on the NA. The internal structure of the pistons is also different, the TT ones have a hollow ring inside the top that fills with oil for better cooling and a thicker dome towards the center. Oil pumps are different. They mount the same and are the same internally except for the spring for the pressure valve in the TT one is tighter, so it produces more needed pressure to circulate oil to the turbos and cooler. You can actually just change the spring to the tighter one. 6.Oil filter bracket on a TT is different (longer) because it has an outlet that accommodates the hose going to the oil cooler. There is a spring loaded valve in the bracket that will not let the oil circulate to the cooler unless there is sufficient pressure. And then there are the spring loaded ball check valves that let oil bypass the oil filter if there is a problem, these are in the block on an NA. Oil filters are all the same. 7. Cams, Lifters, and valve springs ARE the same (90-93)(same Nissan Part #) The Auto TT has different intake cams (lower lift) but the intake cams on the 5 speed TT, NA, and auto NA are the same. The different intake cams in the auto TT along with the slightly smaller exhaust housings on the turbos results in 20 less HP in the auto TT (it was detuned to make the transmission last longer). All the exhaust cams are the same. The 94-95 cams were different than the 90-93 but just like the earlier ones they are all the same except for the intake cams on the auto TT. The 96 cams were ALL the same. 8. The valves are all the same size. But the exhaust valves on a TT are made from a stronger alloy (iconel) 9. Nissan claims the bare heads are different but I no longer believe it. I used to think the thickness was different but after some measurements I believe they are the same and have been using them interchangeably (just making sure the exhaust valves are the stronger TT ones) or just using all replacement valves which are usually made to TT specs, with no problems. We use different spark plugs on the NA and TT, but we see them used backwards and every way in between a lot. The TT ones we use are NGK PFR6B-11B which are slightly longer that the NA PFR6G-11. The longer plug is "colder" which helps with preventing detonation at higher boost levels. 10. The oil pan is different because the TT one has 2 tubes protruding on the sides where the oil return hoses for the turbos mount and another one for the hose returning from the oil cooler. 11.The turbo engine obviously has a few different accessories and systems to accommodate the turbos. The exhaust manifolds on the TT are much shorter than the NA ones, which go all the way down and tie into the exhaust section including the catalytic converters. The turbos are oil lubricated and water cooled. So there are oil and water, supply and return lines everywhere on a TT motor. 12. The throttle bodies are the same size but the passenger side one is different on a TT simply because one of the water lines attached to the bottom of it has a junction in it to feed water to one turbo. But we usually do away with all that nonsense with the water lines under the plenum running to the TB's in our warm climate. We just run water to and from the metal hoses on the back of the motor going to and from the heater core. 13. The upper and lower intake manifolds are the same TT and NA 90-92. The newer ones are different from the earlier ones. They made the change to the new style injectors, lower plenum, and the intake port on the heads in 93 for the NA but not till 95 on the TT. So lower plenum and heads would be different on 93-94 NA and TT's. The upper plenums changed just a small bit in 94 when the angle that the flange of one of the EGR tubes bolts on to the plenum rotated about 30 degrees. Just enough stuff to make interchanges a pain. 14. Motor mounts are the same, but I have a secret on that. I guess I'll let it out if you've read this far although I have made some money because of it. The convertible motor mounts are the same but substantially cheaper for some reason. Motor mounts are broken into almost every time we pull a motor, so we go through lot of them and have saved $. 15. Head gaskets have a different part # but appear to be the same we use all TT ones because they are cheaper also (another secret). 16. Water pump, PCV valves, exhaust, intake, plenum, valve cover gaskets, seals, Timing belt, thermostat all the same.