Rearend swap

I know someone that has a chevelle rear end but he said that you had to change the spring mount. or something like that. Anyone have any insight into that?? Or what rears will bolt right in to the 1st gens.

Chevelle rears are coil spring cars and are too wide for a first gen. A 10 or 12 bolt from a first gen or a pre-75 Nova or equivalent (Omega,Ventura,or Apollo) is needed.