I'd say ISF, out of the choices listed b/c it's a nice platform that hasn't been done many times.

IMO, a good project car for a shop is one that as new(er) and hasn't been done 100+ times already. It show's how that shop does things, and it'll also grab more attention then say a R34, that's been done a million times over. There are a few choices listed that fit that criteria, so I'd be happy to see that. Good luck with whatever you do, I'm sure it will be nice.