Again 100% behind Nismoid,
I was the same as you, bought a basically stock R33 GTR thinking I didn't want one to molested, then not long after looked at doing mods $$$$$$$ holy s**t your blast through the cash real quick..
So got rid of of stock one and for about $6K more bought one with 2.8L and everything, about $50K worth of mods, you never get that money back..
As said if its built, just make sure it was done by a reputable workshop, and get it checked.
Look in the for-sale section here, there are always bargains and you can usually find a bit of history on them, lastly do a lot of tyre kicking and look at heaps