O.K, some info on the 368 valve train setup.
The bolts that mount the rockers are 5/16 inch. The bolts go into the head 1/2 inch.
Valve spacing is the same for all Cad big blocks. Rockers are mounted on hardened U-shaped square pedestals which tie the intake and exhaust together for strength. The solenoid ones also are tied together on top .
Potter's bars may not work because the stud is at least 3/8 which is too large to mount the U-shaped stands. If the stud is removed the hole is already too large. Also the heads of the mounting bolts for the bars sit above the surface of the plane that the U-mounts must sit on. The U-mounts span these mounting bolts which happen to be between each set of valves.
Perhaps the U-mount could be cut in half on the base and then clocked away from the plate mounting bolt.
Also to restrengthen the setup aftering cutting the base a top ty-bar like in the old's engines could be used.If a person got really inovative a girdle tying all of the rockers together might work because the 5/16 bolts are pretty light.
This system is certainly do-able given a little time.