Fenderwell headers, small block, "A" body
A little history as these are cool oldschool units.
Had to research these a while ago figuring out what these monsters where on my 65 Dart project,
Headman headers bought out JR in the early 80's. The guy with jr still worked for headman until no compete clause ran out then started m&d headers which became mad dog headers.
These units will make serious hp.
In dealing with my project have found out in an early-a all you need for exhaust if so desired are 6 " collector extensions then 45 degree bends
and go from there.