Jordan,
from what you've told me, I think you should try once more to start your old motor before jumping to any conclusions. I'll repost there soon, but read TOHcans post carefully- good advice. Take your time, go step by step, and post your progress in detail. If this motor can be started, we can start it for you.
If it can't, and/or you are in a hurry, Bjorn's advice is sound. If you're not looking for top performance (which will cost in both dollars and wear and tear on your drivetrain), another 2 barrel Pontiac 350 would be fine. You'll probably find someone on this site, or nearby, who would be willing to part with a used, running 350 because they are anxious to put in a 400 or 455.
For that matter- don't rule out a 6 cylinder.

Based on what Ken has told you, changing to Chevy will require modifications and changeovers, as well as additional costs for all the accessories that will far exceed $2k.