360 4-speed set up

Thanks for the info guys.
I found this link...
http://www.slantsix.org/articles/4-speeds/ODA833fourspeed1.htm

Here is a quote:

The Overdrive bell housings can be modified to accept either the 4.80" or the 4.35" IBR. A ring must be fitted to the bell housing to reduce its IBR hole from 5.125" to 4.35" or 4.80". This ring must maintain the hole's exact center! A skilled and caring machinist should be able to accomplish this without issue. Good planning would provide the machinist with the bell housing and IBR you plan to use so a perfect fit can be achieved