The 71 Dana case is not weaker. He means the carrier, Probably. I can see where it would be weaker. It’s an open design. Your problem is going to be axles. I’m pretty sure if you put in an older power lock in your 71 housing, they will need to be a different length. The 70 down power locks have a pin in them that holds the two cross shafts of the suregrip together. The axles touch those pins and that’s how the axle play is adjusted. The 71 track lock looks totally different. The power lock that is currently produced, does not have the provisions for that pin because the cross shafts are not drilled. You would have to use green bearings to solve that. DoctorDiff probably has a suregrip to fix all this and knows more than anyone about interchangeably on these so give him a email. He’ll call you back.