Breaking motors
It sucks when you lunch one. That's the one thing about this I fear. Unless you have alot of spare money, parts or, best case, complete motors. A catostropic failure can set you back for a goodly amount of time.
Just hope you can salvage some of the parts. Just from your description, sounds like a lack of oiling. Did the lifter sieze in it's bore? When pushrods bend and/or break, they can do some nasty things. That's another thought, was the pushrod itself oiling, or might it have clogged.
If the motor had alot of use as you alluded to. It might have just been a parts time to fail.