The replacement gears for that rear end are3.38. You probably have 3.90 in it now. I don't know what your tire dia. is but I don't think a 235 can pull any higher gears then what you have. If you gear it too high it is unpleasant to drive & will get worse mileage. You might look into the engine for better mileage. Advance the timing a little & make sure the advance mechanism's are working. Check the carb for running rich.
