Set new engine up help?

well it runs and timing is OK but having damn carburetor problem I bought a holley 600 mechanical double pumper I'm having nothing but problems with it from running to rich and leaking gas ready to through it in the garbage. LOL but unfortunately i bought it new and that would be a waste of money.
I need a good bolt on no fuss street carburetor for a 340 4spd mostly stock with headers and aluminum intake any suggestions or on you put on with no probs?
thanks for any help