The biggest visible differences between the 1968-72 & 1973-77 GM A-body frames is gonna be the shapes of the front suspension control arms and that the frame horns on both ends of the newer car are enlarged for the bumper impact absorbers. I can go look to be sure but am thinking that the 1973-77 frames don't have that little skid plate under the first crossmember as on the AMT 1969 442.
Also, dual exhaust was dead starting in 1975 so you'll need a single hump transmission crossmember.
Fun fact: after the 1977 A & G bodies ended production that same frame then went under the RWD 1977-96 B & C bodies (Impala, LeSabre, Delta 88, Cadillac Brougham, etc)
Best option might be the Revell 1992-93 Caprice. It will have the right frame, suspension, floor pans. And it should have the correct tranny crossmember & exhaust system.. Dual exhaust made a comeback in 1994 so next best may be the Revell 1995? Impala SS. It will look right except for the dual exhaust crossmember & pipes.