Input Bearing Retainer Question

Well, I talked to Jamie at Passon.... I have a 1972 tranny with close ratio gears(I took the cover off and counted the teeth on the gears). It has a 5 1/8" retainer with the small bolt hole pattern(Jamie said he doesn't sell too many of that style retainer),so I just need a 4 1/4" retainer and I'm good to go or I can get a bellhousing with 5 1/8" opening. That way,I can switch to an o/d tranny and not have to change to a smaller hole bellhousing...Thanks for the info...Dan