are these truck rears?

I would agree, if they are the bolt-on drums, they are not up to par with the newer ones. I had one like that in my 50 DeSoto, I snapped the axle shaft with the flathead 6... Sometimes, that old stuff, even if it is cheap, free, or laying around is not always worth using. I also believe the splines on the inner end of the axles is different than the newer ones.