I'm in the same boat with a B body. Not sure if they will fit an A but found these.
1974 DODGE CHARGER MagnaFlow 19343 MagnaFlow Performance Manifold Pipes | Summit Racing
I don't even have a mopar anymore but I still check in here just about everyday. I've met some good and smart people from here and got some good deals and parts along the way.
Rockers cost about the same. So we are talking about carb, intake, cam, and headers. All things being equal, in my experience, the 383 will destroy the 360. Just don't over cam it.