3spd to 4spd?!

I think both transmissions are 23 spline input, and if both bellhousings are for the same size flywheel clutches are the same. bellhousings usually have dual trans. bolt patterns. measure the diameter of the opening in the front of the bell, probably 4.3" or 4.8" , and the diameter of the OD trans. front bearing retainer is probably 5.1" The larger 5.1" can be turned down to 4.8" . the 3 speed and the 4 speed OD both use the same 26/27 spline output/yoke. I think both trans are the same length, and the same length as 904/727, so an A body/8.25 driveshaft fits.