My '64 C-10 has a Rochester Model B carburetor. The truck gets terrible mileage (10 mpg), the plugs are sooty with 1000 miles on the newly rebuilt motor. I've talked to some carb experts that are split on what to do: one says convert to a MonoJet, the other suggest that the rebuilt carb has the wrong jets and that the only solution is carefully rebuild the carb, and experiment with smaller jets. Any suggestions?