Build the 350, a mild cam, a good intake and carb and free flow exhaust should be well under your 5K budget and be a healthy package.

The stroker engine in HPP is also pretty straight forward, the cast 4" stroke crank, should you go that route, saves a lot of $$$ over the aftermarket forgings, which you shouldn't need anyway.
Running larger valve Pontiac heads on a 350 you'll have to watch your cam lift, but a mild performance street cam should pose no problem. A 383 Pontiac should be a screamer, I plan on building one for my next project.