1970 carter 4933s,Rebuild or buy edelbrock?

First off, have you determined that the carb is even the reason that it "runs little ruff"?
A little discoloration at the carb seams doesn't necessarily mean that it's leaking. I would definitely rebuild the original Carter (it's already an AVS, by the way) if for no other reason than to get gaskets and seals in it that are compatible with today's fuels.