What rear is this?

Now this brings me to the next question. I have another more traditional 9 bolt 2 1/2” tube 7 1/4” that is BBP out of a 1975 valiant. Will a SG out of a early model like a 65 or 66 7 1/4” fit the 75?
I think it may be worth trying, because the second Gen 7-1/4 (at least the few I’ve dealt with) had positive axle retention. It may be best to locate a scrap big bolt pattern unit to disassemble to check, though. I think there was an axle spline drive angle change when they changed to a C clip axle, but not sure on the second Gen unit.