Why do I keep breaking rocker arms?

I finally have a couple photos and a little more info. So the mechanic is sure that this break is the result of over revving leading to valve float. I've certainly gone into the 5000s some and do tend to drive fairly aggressively. Mech wants to install a rev limiter, which feels sort of like training wheels, but maybe that's what I need. I did read an article about valve float that implied better springs would help guard against it. I'm pretty sure that the pistons, rods, springs, etc are all stock. Do I need to get high performance stuff to safely hit 5000-6000?

On another note, I finally had the chance to try out the distributor I got from @halifaxhops. It's incredible how much better the car drives. The man deserves a trophy or something.

IMG_4203.jpeg

IMG_4204.jpeg