Nope, too new. The 68-70 340 manifolds are the first choice and the 71-74 manifolds are next best. There are combinations of LA and Magnum manifolds that work well too. There are many threads here on FABO about all those choices. Yes, if the headers are in good shape I would probably leave them.
I have been going through and trying to read as much as I can. Sometimes it’s gets a bit overwhelming with the headers vs manifold debate. Sometimes I just may not be searching in the right threads either I am sure.