Bob:
I don't know what flanges you have but adapters are easily made by any machine shop.
The adapter bolts can be fit from behind the flange, and then the CV simply bolts up on the front side.
The existing flanges on your box should have a counterbore that will self center the adapters,.
Just remember to use safety wire on the bolts, if they back out they will really tear up the side cases.
Good Luck
Phil