Need some help controlling body roll

It looks like you have the same wheels as my orange car from looking at the pics of your welcome aboard thread Big bolt pattern. I am not positive but it looks like you have a B-body rear in the car. You will need to get the total width drum to drum and see what rear is in the car. One thing to remember is if you have Big bolt axles in the car with a duster rear. It will be 3/4 inch wider

All measurements are from drum to drum: Sorted by length
1966-1972 A-body 57-1/8″ (what your car should be)
1962-1963 B-body 58-1/2″
1964-1967 B-body 59-1/2″
1970-1971 Imperial 59-3/4″
1968-1970 B-body 60-1/8″
1970-1974 E-body 61-5/8″
1965-1969 C-body and 1965-1970 A100 Vans 61-3/4″
1965-1966 Imperial 62″
1967-1969 Imperial 62-5/16″
1970-1971 C-body and 1971-1974 B-body 63″
1965-1971 D100 pickup 64″
1969 C-body wagon and 1971-1973 B-body wagon 64-3/8″
1970-1973 C-body and 1972-1974 D100 pickup 64-3/8