Glenn,
The plugged passage is usually a pretty easy 'in place' fix. If your rig has hydraulic lifters then I think a tube runs from the rear cam journal up to the center oiler. This small tube and its related fittings plug quite easily.
The pushrods would never actually be 'too long', but the geometry would be thrown off where pushrod meets rocker and rocker meets valve stem.
This would probably be minor and not cause problems. Although I don't know for sure, I think the head would have to have seen full out drag race service to have been milled too much.
A automotive machine shop would remove the least amount of material necessary to clean up a head. The 'clay in the combustion chamber' trick is the last word in determining clearance issue inside the engine.
It would be interesting to put a rocker arm in a vise and see exactly how much abuse it took before it broke. This is a very intriguing problem, and I hope you figure it out and share the results with us.
Stuart
