I know for turbo's you can't have a high compression engine. Im just wondering if blowers are the same way. And how much engine reinforcement am i looking at for putting a blower on a 350 from 1981. It's got stock 8.2:1 compression.

Blowers are the same way.

How much reinforcing do i have to do to be able to handle a blower? I just want a small one that will fit under the hood without modifying the stock hood. Im getting new pistons, heads, etc. Pretty much a whole new top end. Is that enough?

Low compression Forged pistons and Fel Pro Racing Head gaskets should be enough.

Cool, and do they make superchargers that will fit under the hood of my car without poking through? Its a 1981 with the stock air induction hood (which i want to keep).

I doubt you could fit a roots style supercharger under a stock hood. The Vortec would be a option for you.