Bushed? Are you sure about that? I ask because the ones I have purchased (and I like them) have the aluminum body running on the rocker shaft, as do the Hughe's rockers.
I ran Cranes way back in the 80s with aluminum riding on the shaft, but the Mancini rockers looked like regular Harland Sharp rockers with oilite bronze bushings instead of caged needle bearings. I don't own them, just saw photos and an analysis of them when they came out.
