1. You know nothing about how the car was driven!
This is true for any used car you buy.
2. If it was run like hell on the track - you don't know if the engine needs rebuilding - NOW.
Why I said to do a leak down test and get a PPI
3. It's already got an engine that didn't come with the car!
Only an issue if he wants a garage queen, there are some examples of peoples cars that have new motors due to harmonic balancer breaking/rebuilds...NSXTASY comes to mind...if you could source a good engine for less than a rebuild might be a reason he has a new motor.
4. This has all the ear marks of a bad deal for you - in my book.
Tim, based on all your posts, when you were buying an NSX, you wanted a pristine NSX that was not modified or lightly modified if that, so this car is obvioulsy not for you. The OP may have a different opinion about what they want in a car, maybe a cheap way to get into a turbo car if they wanted to go that route, assuming it was built properly.
5. Is this guy a Prime member - if so have you checked out his threads. If he isn't - you can't check him out and this car needs some serious checking out in my book.
Agree
6. Based on the cursory research you've done - if I were you I'd move on!
As I said, depends on what the OP wants, do the Compression Leakdown test and the PPI and go from there if you are still interested.