Husker -
I just found you yesterday (the hard way) about the staggered valve cover bolt holes. I picked up a set of chrome valve covers at a swap meet, cleaned them up, and they didn't fit for just that reason.
As far as valve covers themselves go, I think you'll be stuck using original steel ones.
I got my gaskets at Napa...I just asked for gaskets for a 1975 350. The ones they gave me were some kind of black stiff rubber, and they were set up to fit either the early offset holes or the straight holes. I think they were $10, Fel-Pro.
Chris
