Some of the Olds and Buick stuff in the 70's was .I once orderd bearings for a 70 Pontiac Firebird with a 10 bolt C clip rear.
I picked up the parts and when I got home it was the kit for the "semi floating" rear axles that used the bearing retainers.
Had to take it all back. The book showed two part #'s available. The shop manual I was using even had a section describing the service for this type of diff.
Whether or not it made it as far as 1977 ? I dunno.
The reasons for the aluminum drums was 3 part:
Mostly Weight savings when GM was grabbing at straws to hit CAFE standards.
Cheap source of recycled aluminum for manufacture.
Slightly improved fade resistance due to improved heat dissipation.
These were on light duty cars.
I do not know if they are still available in aluminum as an aftermarket or dealer replacement.
A check at the parts store will tell ya that.
I'm guessing NO.
Mic. those aluminum Drums real good before you leave the yard to se if they will even clean up. Check them for bell mouth / taper and run out.
They may have been prone to warping.
Make sure the balancing buttons / weights have not been knocked off or damaged.
Missing or broken fins can cause out of balance.
Consult Hollander Interchange Manual to be sure they will swap to your particular application. .A yard worth their salt should have the Hollander database at their finger tips and the people that know how to read it.