My model A wont go faster than 40-45

[Sparta]

Hey guys! I’ve got a bone stock 1931 ford model A. It has a rebuilt engine with steel valves and bearings instead of Babbits. I just out on a rebuilt carb trying to solve the issue, which solved my backfiring issue, but car is still sluggish. The previous owner mentioned that the timing was off and that he fixed it before selling me it. The idle isn’t very steady, meaning it has intermittent hesitations when idling. Other than that, what else could it be? Could timing being alittle off cause the car to top out at 40?

Thanks