The Pontiac engines are well supported in the aftermarket. No worries on getting parts.

If you're going to be driving this ALOT and you can't find a Pontiac engine, then I 2nd the GM LS engines. They are a more expensive than a Chevy smallblock, but worth it. They are extremely efficient, make tons of power with ease, easy to drive, and are very durable. I'd rather see one of these true Corporate engines (designed from the ground up after GM Powertrain was consolidated) in a Pontiac, than a Chevy engine. The swap might be a little pricey, but you can keep costs down if you find a take-out setup from a junkyard (make sure you get the wireharness and ECU), and keep the modifications to a minimum (camshaft and headers are all you need to really wake them up).