B body small block Bell question.

What model is the three speed? I know the NP A230 used the same 1 X 23 spline input shaft as the NP A833 and on the one I used to have the front bearing retainer was the same diameter as the one of the smaller size input bearing retainers used on the four speed. It was a 3 speed truck transmission. The construction of the 230 was almost a direct descendant of the A833, it was so close that the tailshaft housings would almost interchange. Measure your bell housing front bearing retainer register and compare it to the four speed sizes, the one that I know will not work is the large overdrive four speed bearing retainer, measure your input shaft length if you still have the old three speed. If worse comes to worse, some bells I have seen came with enough material to have the bearing retainer bore machined to a larger size, and advance adapters at one time made spacer rings that can step the bore register down to smaller to a smaller size, if need be.