Which bellhousing to use?

Not sure what parts you mean? The trans. will bolt up, its just the fact that the bearing retainer on the trans. is 5.125" and the most common bellhousing I am finding is 4.80". I would like to find the O/D bellhousing, but havent been that lucky. Anyone know where to purchase the smaller retainer and how difficult it is to change?
i think i have one that im not gonna use ile measure it. let me know if your interested. $50.00 shipped to you.