The rearends look the same, but there is a slight difference in the angles of the control arms. It is not a bolt in swap.
If I remember correctly, somebody makes control arms for the swap but I think it's to put chevelle rear in a G body. I don't think anybody makes it swap the other way. The whole point was to put a 12 bolt in a g body. Nobody with a chevelle should consider putting in a G body 7.5" 10 bolt. And if you have a 8.5" 10 bolt for a g body, plenty of people will pay good money for it so you could sell it and buy a 12 bolt for the chevelle.
81 Grand Prix, 355, 700r4, 8.5" 4.10
64 Oldsmobile Jetstar, all original