That is a great looking Formula!
As far as powering it, I don't think keeping what I am assuming is the original Pontiac 400 makes sense due to the other mods you're planning for the car. If you're going to do 750 hp forced induction, I think the better choice is to stick with the LS / LT platform. The aftermarket support for the Pontiac engine is the best it has ever been but it's nothing like the LSx support.
I went with an aftermarket Butler aluminum 505 Pontiac based engine with multiport EFI for a planned 600 hp / 600 tq, get it under the stock Formula hood and add a little weight savings to the mix.