Personally, I can't see pushing more than 7-8psi on a stock block. Anything more is taking a risk that I wouldn't want to take if your on a budget.
As 1turbofocus had mentioned, tuning is the key when it comes to forced induction. I've seen a few too many engines grenade from lack of a good tune.
My thought is if your going to shell out the cash to do a turbo engine, then save a few more bucks and build the block as well and have the peace of mind that it's going to last. Otherwise, grab a bottle of NOS and spray the hell out of the stock engine till it blows and continuously replace the engine with junkyard engines.
Fast, cheap and reliable aren't usually in the same sentence.