37's are really to much for IFS IMO if the rig is running the trail a lot, especially with both diffs locked.
I haven't ever seen where an extra inch of ground clearance made any difference at all on the trail, nothing a different line or a well placed rock wouldn't fix.
I think given your trucks dual duty, the added weight of the 37's and the power needed to turn them, along with the added stress this puts on the IFS, you would be better off dropping back down to 35's.
As to the 22r turning the 37's, if you rebuild the engine, you should be able to turn them easilly enough, providing you have 5.29'
