I helped
@Turbo440Dart replace a timing cover on his duster with a 360 and I believe he got a Mancini repop cover. It was a nightmare to install but using the oil pan bolts to pull it down solved the fight we had with it. You can read it in his thread here;
Dumpster diver 70 Duster build
Hopefully he’ll chime in and correct me if I’m wrong.