Tried to post in performance but locked out. The Cadillac 4.9 has stamped steel rockers bolted to an aluminum support bar, with aluminum pivot/bridge holding each pair together. At high RPM the steel bolts rip out of the support bar holes (fixable with helicoils), and over time the rotational stress also causes the aluminum pivot to snap. Both are very common failures when the engine is pushed. I bought new supports and pivots when I swapped engines, and broke one of the new pivots a few weeks ago less than 5k miles later.
I am trying to come up with some options for stronger pivots. There is nothing aftermarket for these engines so I may need to adapt something, or change to a different style. 1.6:1 ratio not terribly uncommon
Sealed Power has these old rockers that look very similar except a 2-piece pivot and bridge, but the bridge is straight instead of off-set. If I could find/make off-set bridges maybe that would work
This 4.9 build in a Fiero used some pedestal mounted roller rockers, but he machined the support bar to keep them from twisting. Old thread and the OP sold the car to somebody else so can't ask about it.
I was looking at some roller rockers with a center bar and it looks like the box stand could be bolted into the support bar
Comp Cams has a few designs, same hurdles as the above, need to stop them from twisting somehow