Magnum heads

I have the Crane roller rockers for a sbc on my magnum heads. I used Hughes guide plates and 3/8 studs, which is a lot better than the Crane kit. The Crane kit has plastic pushrod guides which do come apart.
I had to put lash caps on the valves to get the rockers to roll across the tip properly. With a 8mm stem you don't have much room for error.
If I had it to do all over again, I would just get the Hughes kit.