I just went throught the very same thing you did. And guess what? I was running the Stainless steel rockers with edelbroock head. had a cam research cam that was broken in before I bought it. 242 and 242 with 590 lift. The push rods were ball and cup design.
DID YOU CHECK YOUR DISTRIBUTOR GEAR?
Mine was worn down to a razors edge.
After pulling the motor and replacing the Cam witha new pre boken in cam research cam had a race car shop install the motor and break it in. 20 miles and the rockers threw a couple of push rods. Ended up pulling the entire rocker assembly and push rods and replaced them with a precision
oil pump set of aluminum rockers and ball on ball push rods. The aluminum rockers have better geometry and supply more
oil to the lifter area. These stainless rocker I do not believe were designed for edlebrock heads but hey if someone wants them. They are for sale. have less than 60 miles on them. They were the supplier to Shelby and beleive they were set up for the Shelby heads.