I'm looking at changing direction from using my unused Hedman Elite headers & go to manifolds. I would like to go with the ones for '64-'77 cars. I want to use the Pypes DGU14S down pipes but Pypes tech seems lost when I asked if they would work in my '81 using the earlier manifolds. Even after I told him some '78's had the earlier ones. Just so every one understands why I want to go with manifolds is that I just got a '70 L48 350 that may hit 300 real world horses with manifolds, more horses than I was expecting.