Well, I was pondering this this a while back, and you could do it fairly economicly, probably in the $10-12K range if you do your own work.
You start by finding a core 3.2. Get the heads modified for twin plug, send the cylinders to EBS to get bored out to 98mm (for 3.4 liter), with a new set of JE pistons, at about 8:1, with at minimum 964 cams. You need to relocate the oil tank forward like on a 72 (or Yellowbird), to make room for the right side turbo.
For exhaust start with Bursch headers and move the flange back toward the collector and fabricate a short pipe to the turbos, with the exhaust continuing to a custom flowmaster (or similar). Or try and adapt 993 TT headers, but they would probably cost more.
I don't know enough about turbos to know which ones to use, but there are certainly off the shelf components that will work, off any number of different cars. I wouldn't limit myself to Porsche turbos. There is a lot of turbo knowledge with the import guys. Who knows, Supra twin turbos may bolt right up.
For induction, use the stock 3.2 manafold with a aftermarket EFI (Motec, Haltech, etc). You would still need to come up with a boost controller of some sort, oiling for the turbos, ARP hardware, and probably a bunch of stuff I haven't thought of. The hardest part would be mapping the EFI.
Of if you are really talented like Mark Hargett, you can fabricate the whole thing from scratch.
http://forums.pelicanparts.com/showthread.php?threadid=130267
Tom