There are 4-5 different gear ratio available in the Saginaw 4-speeds...they are all direct drive transmission with 1:1 high gear, the same as the 3-speed you're probably replacing. The difference is in the lower gear ratios. The input shaft will have rings/grooves machined around the shaft that tell what gears are inside. Post the number of rings/grooves and we will have a better idea if that's a good choice or not.
Mike B
