Well sometime soon I will be trying this. I’m picking up a 8 1/4 with a 2.25 open. I’ll be attempting to install a SG and a 3.21 or 3.55 in. I’ve questioned the two housing theory and never bought into the different housings.
Let me know how that goes. I'm in the same situation, but will probably go with 3.23 gears. It has 2.2 gears now.
It is a later model 8.25, from a 1989 Fifth Avenue. I was told by numerous FMJ members that it HAD to be a 7.25, since "Chrysler never put 8.25s in Fifths." Bought it from the original owner who claimed the car was all original. To me, the housing looks just like every other 8.25 I've seen.