Bob Mullen did some road race hemi heads for us
they later had a "D" number but I forget which
more torque
Colt
also contact rocker arm specialists in Anderson CA
They make or made case oven case hardened deep heat treated shafts with or without triple chrome which required grinding undersized then copper, then nickel, grind, then chrome
They left LA area about the same time the Air Quality people were coming down hard on the platers