Chevrolet sells a New (not rebuilt) Goodwrench 350 4 bolt for $1,300.
It is their most popular crate motor sold. Your local Chevy dealer sells it I'm sure. To me, that would by far be the best bet.
You will need to put an intake manifold on it and carb, and distributer. You can take these parts off your old motor without any problem.
Darren