You can find 383 rotating assy's for around $500. If you're on a tight budget and your block is in ok shape you may be able to get by w/o any major machining. Hone it, gauge it, throw it together. You don't need a balanced rotating assy for a low RPM street motor. Add some Vortec heads, performer manifold, and a decent cam, probably somewhere in the 246-262 range, possibly with a little extra duration on the exhaust. Get the most current grind you can, it will be worth quite a few HP over the earlier ones.
If you're on a tight budget, rebuild the 350 you have and throw on some Vortecs and a new cam, stay closer to the 246-252 side of things with the duration if you're not stroking it.
1: It's all in the heads and cam combo, so get the best you can afford.
2: There is no replacement for displacement.
If you're willing to do a little parts hunting, you may be able to find most of the parts you need on Craigslist or in the classifieds.