Not all craters are created "equal". Be careful. "Price" shopping is also not always a good idea. Cheaper is only better if you HAVE to have "cheaper" due to constraints. With a '77, you have some pretty early iron there. You can build it "cheap" or you can build it "nice". Pretty tough, even for a Chevy these days, to build a nice one cheap. Only you can decide what you want. If you have future "plans" for the car as a performance or "show" or "cruiser" or any other specific application, buy an engine that fits into that plan.
There are GM craters in a range of performance and price. Most of the 300-400 HP versions I've seen were pretty good. Some of the "bigger" ones have shown piston and bearing issues if pushed hard. A forged crank is always a good idea with the small block. There are other large companies building "crate" small blocks. Most are at a much higher level (and therefore, cost) than the ones you see from GM in the mail-order houses. I've been in one Edelbrock 383. Pretty nice work. He leaned it out and burned a piston. Tuning problem, not engine problem.
The point is, pick what level you're heading for, and buy appropriately. If your budget can "stand" a higher priced, more powerful engine, and that strikes your fancy, don't think the GM is necessarily higher quality. Dart, World, etc. all build GOOD engines.
As heavy as the '77 is, consider a 383. It will have better drivability combined with performance.
I build "customs", and don't sell craters. I offer this from what experience I have with freshening or "cleaning up" craters. I do know, the cheap remans aren't a good risk.
Jim