problem

If these are parts have not been previously bolted together, I would guess that you have a transmission with a 4.80 inch diameter bearing retainer and you are trying to put it into a bell housing with a 4.35 inch opening (see brian6pac post 3). You may luck out and find that the previous owner of the transmission put an adapter ring around the 4.35 inch bearing retainer to make it fit a 4.80 in bell housing. In that case, you can just take it off.