Is a 7.25 rear strong enough?

Does anyone make one of those mini locker type of differentials for the 7 1/4" axle?
Also....Is there any differences between the years that would prevent one from swapping axle shafts to change a 4" bolt circle axle to a 4 1/2"?
You know, like a 73-76 V8 front disc car axle as a parts donor?
I've always just defaulted to the 8 1/4" or 8 3/4" axle but with those can get costly.