I bought the black mopar performance valve covers for my 440. I also bought the grommet kit. One grommet has a large hole and the push in breather fits in it. The other is a smaller hole, maybe 7/16" in diameter. I assume it is for a PCV valve. What PCV valve do I get? Were all the PVC valves pretty much the same in the late 60's and early 70's? Thanks. Bill.