what I would need to swap a 400 into a 87 tpi 305 car?

[Bipolar]

And still be able to use my TPI setup?

[five7kid]

A very, very mild 400!

TPI just barely lets a 305 breathe enough. 350's were severely restricted. If you upgraded the entire TPI with aftermarket, higher-flowing base, runners, and something like a 52mm TB, and ported the plenum, it would be better. To really let the 400 do its thing, though, would require something like a Miniram, Super Ram, or Stealth Ram.

Of course, if you stuck with stock 400 heads and a mild cam, the heads would be the flow limitation, not the TPI. :D

[Turbo-Zone.com]

I have the Super Ram base intake if you are looking to get a head start on parts.

[Trevor86TA]

How mild/wild of a setup do you want?