What car would you build?

Yep.

$2k-2.5k (last I knew) for Turbo or SC, $3k or so for a full VQ35 swap (slight built so it can handle some HP - 2002+ Maxima) and a couple other hundred(s) for things like exhaust, etc. Another $2k-2.5k if you decide to go 5 or 6spd.