I'm using the original rocker arm springs that came with the set.

After measuring, if I take .080" off each side of the aluminum hold-downs, the pad will be centered over the valve tip, and only thin shims to provide something for the iron rocker to ride against other than the aluminum.
IF they fit under the MP valve covers that is. Otherwise it's back to the stamped steel (stock) ones!

Incidentally, my cam is a slightly reground (to restore lobe taper) Mini-Express with mushroom tappets. It was 278/.654, now 272/.652 with less (.018) lash.
I bought the rockers from AndyF at his recommendation - valve springs are Comp 953 with 130 seat, 430 open as previously mentioned - so I don't need high-dollar rockers. Yet