All depends on what you want to do. Lots of very good options out there.
As mentioned, a properly rebuilt Qjet is a very good option, but you would want to have ALL of the factory components in place to make it work perfect.
Otherwise, there are several aftermarket carbs out there that work very nice. I'm running the StreetDemon 625 on my SBC, and I believe they recommend the Street Demon 750 for BBC applications:
https://www.holley.com/products/fuel...mon/parts/1903
I've been impressed with the easy setup, smoothness, and easy starting I get with mine. It was inexpensive compared to some others, looks pretty good, but most importantly works well.