I just thought of something. . . The 722.3 / .5 have a one piece case ( built in bell housing ) so there won't be a 722.5 with a V8 bell unless there was a very rare build I haven't come across.

The M103 / M104 straight 6 and M110 4 cyl pattern was made in the 722.3 and 722.5 so swapping there is possible.

But, there is still hope for the 5 speed V8, use the .3 case and add the .5 OD unit / tailshaft / valve body. This all assumes that the main case is similar enough between the .3 and .5.