I have a 66 mustang coupe with a 289. I've been trying to find out if the following transmission/bellhousing will fit without much success. All I know is that it's a 3 speed that was originally attached to a 302. It has the following numbers on it

Casting number on the tail housing: R LA OF A
Number on Case: CC LR OK
Metal Tag: RAB AG EG8
D5IRLA 2520

 

I would confirm it was attached to a 302 previously. If so, find out if the 289 and 302 have the same bolt pattern. My guess would be yes.

God luck.