The Stovebolt Site Forums The Shop Area General Truck Talk Tranny or rear end??

Have a 41 Chevy truck 3 speed shortbed and only get 42 miles an hour out of it. Would like to get it to 50 or 55. Would I be better off to change the tranny to a 4 speed or change to a 3.55 rear? Thinking the rear end now is a 4.11. Have people tell me both. Thanks