hey guys i am running a th350 tranny in my 53 ford f100 with a 10 bolt rear ,,now i checked it and the drive shaft turns 3 times to the tires 2 times .. i am running a 255 tire in the rear ,, i am tring to get my speed-o right right now i am running the white gear inside tranny ,, can someone add to what i need to do please

thanks