the cheapest thing OP can do is find a running magnum, and carb it, which between intake and carb still would be well over the original target price unless he lucks out at a swap meet for the magnum intake that edelbrock wants $400 for these days.
or even a "good core" engine that just needed a hone, and re-assembled with a gasket and ring kit...you're talking hours of labor, several hundred in parts, and then....you still have a stock, no warranty, cross your fingers engine.