I was in the same dilemma mate, do I mod my GTSt or save for a GTR, after much thought I wanted to put an Rb26DETT in my car but after chasing up prices etc on doing this conversion its just not worth it.
Yes I could have done pretty much the whole conversion at home as I have lots of friends in automotive trades and enginering trades welding etc). One company wanted around $8500 for an R33 halfcut. At the end of the day its still a GTSt with an RB26, yes no doubt it would fly but If i want the motor so much I think its a better prop to save and buy an R33 GTR, as I also wanted to paint my car midnight purple, hell, By the time Ive done all those mods including R34 GTR wheels it would have cost me a fortune.
So Ive decided to leave my car how it is, it is lightly modified, suspension wheels etc etc. And save for an R33 GTR in Midnight purple with Rb26Dett! As a bonus I get 4WD, pumped guards, brembos etc etc. And no matter what I do to it, its still always going to be a GTR.
So after my long winded post, keep it relatively stock and save for a GTR in my opinon. It might cost more but at the end of the day which would you rather have in the garage a modified GTSt or a genuine GTR??