The real issue is probably not the OD as much as it is the aluminum housing. The aluminum housing is the weak point of the OD trans.
The gear ratio spacing in the OD trans make it work good for most applications, the OD is helpful with rear gears of 3:55 for lower cruising rpm at highway speeds, and the cast iron case takes a beating. An iron case OD would be a great starting point, if such a thing exists. Gene