I do apologise if this sounds bad, but how long is a peice of string... What vintage engine, which model will it be from, will you re-build it before you put it in, so many variables here its not funny.

However, I converted my B4 to an 04 STi Spec C engine, cost me about 8 grand. Bit more if you include the extras I had done. But doing something like that will introduce other issues. The gearbox for one. Suspension. Brakes.

By the sounds of it, and this will sound repetive, but sell it and buy a turbo model before converting an N/A, especially a Gen 2. I'm not saying dont, but unless you want to keep throwing money at it, that is my very serious suggestion.

Cheers,
Ben