rochester 2bbl jetting

76 is big the problem with that carb is the brass tubes that are made into the venturi wont let the fuel flow they must be enlarged ,I would drill the bottom of the tube larger about 3/16 ,the holly 500 cfm uses 68-72jets on a 355 chevy , when we switched over ,if you enlarge the area around the jet in the carb you can switch to holly jets they are a little wider then the roch. and every body has them ,I had the same problem I think it was in the 80/s but was running 13 to 1 comp.and I was drilling mine out to size.