Why do I keep breaking rocker arms?

Slugfarm said
Specs have been hard to track down, as the rebuild was subbed out to a supposed 'slant expert' in Texas (don't have the name). Texas built the engine with a 'performance' cam of unknown nature and I'm pretty sure everything else is stock.

I'll add pushrods to my 'more info needed' list.

#2 and #5 valve adjusters appear taller because those two valves are lower, which seems odd as one is intake and one is exhaust. I realize that this is a dumb question, but are the valves all supposed to be at the same height?

If the valves are stock sizes, there may be variations in height due to the condition of the head, and chamber casting cyl to cyl. Unless the difference is large, a lot of shops won't do anything to correct this, they simply shim the springs to get the seat load & ht. correct and let the adjusting system handle it(hydraulic or mech.). It's not "ideal", but has been done that way for decades as basic rebuild practice, and performed fine. If the valve has sunk too much, a replacement seat needs to be installed in the head, & brings the stem height back down.
Also, here is a factory adjuster in the cup of a 3/8" Crane Chrome-moly pushrod, they are not tight together.