You need to toss a standard block chevy in it. I'm hardcore Ponatiac, and I destest Chevy products, but I don't see why it's such a big deal!
Also, it cheaper and you get more hp per dollar from a chevy. Treat the car as a Camaro, and it won't cost you one penny more to convert to v8 chevy power than v8 Pontiac power.
Why use a Pontiac 400 than a 350? It costs the same to build eigher engine. A lower hp 400 still has a signifigant edge over a higher hp 350 is because of a thing called torque.