Small Block Bellhousing That Fits 4.8" 4 Speed Bearing Retainer

On the over drive trans only 1975 trans used the 5.125 retainer with the small 307 bearing all others as far as I know used the 5.125 retainer with the 308 large bearing. So the first thing you have to do is find out what input bearing size you have before you can pick a bearing retainer.