Anyone install three speed with overdrive behind a slant six

They made a few early ones with the 307 bearing. You just swap the front retainer for the standard 4 speed retainer. I have converted a couple O/D to standard main housing to fit in the 66 without mods. Does not seem to be a problem.
Lol, page 6 of Jamie Passon's book, "1975-only that used a small 307 bearing and had the large 5.125 inch OD. "