Good morning Casey. Along the way many of us have had experiences similar to yours. It’s probably the origin of the saying “If you want something done right, do it yourself”. Bending pushrods and breaking rocker arm studs requires a lot of force and that force came from physical interference between parts. As others have pointed out the likely suspects are valve to piston interference, valve spring coil bind and/or rocker arm slot too short.

All of those things can be checked without removing the heads. But if the valves have collided with the pistons the valves may also be bent and the heads will have to be pulled to correct that. If the broken rocker studs are screw in types they are easily replaced with the heads in place. If they are pressed in studs it’s probably possible to machine the heads for screw in studs without removing the heads if you use some ingenuity but would you really want to risk machining chips falling into the engine? I doubt it.

There are some excellent “How to” books to help you through this. A couple of examples are:

How To Rebuild your Small-Block CHEVY by David Vizard and SMALL-BLOCK CHEVY Engine Building by the editors of Chevy High Performance. It’s great to have that information to refer to while you are doing the work.

I would bet that when you start carefully inspecting that engine you will find that the guy who put it together made some other serious mistakes also that haven’t shown up yet. The books mentioned above will help you to find and correct the other guy’s mistakes.

Good luck!

Ray