Would it be possible to make a 327 into a tpi? Im just curious seeing as Im building one in the future. Would it give me any gains in gas mileage/performance?

 

Not really. A 327 is a short block, but TPI is an intake system. I don't think it would be practical no matter how much welding you did.

Although, I'm going to take a big leap of faith here, and guess that what you really meant to ask was, will TPI fit on a 327; and the answer is, yes. Subject to the center 2 bolt holes on each side of the intake maybe having to be slotted, if the TPI is 87-up and the heads on the 327 are 86-back, or vice-versa.
That would depend on what you've got now. Kind of hard to talk about "gain" without specifying "over what". But in general, it would probably give better gas mileage, but less performance. In general. Your specifics may vary.