I have a 46 with exactly the same engine and transmission. I would not go over 45 miles an hour. You are pushing it with the old babbitt bearings and cast iron pistons. In those days roads were not in condition to travel much faster than that. There is a kit from Patricks in which you can change the ring and pinion and get 65 miles per hour without high engine RPM's. Remember this though. Your suspension was not designed for those speeds. Do like the good man said keep it at 45 and just wave as they pass you. The speedometer does mark 100 but that is just the way it was printed. Nothing on your truck was ever designed to come close to that speed.

If it doesn't have a bowtie it's just an imitation.