I do hope it is a simple fix Mark have you ruled out the cam followers and push rods ?
I didn't pull the valve covers off. Right now it seems that whatever it was is now out of the gear train and hopefully in the oil pan. The engine starts and runs smoothly. I'll keep going till I find out what it was, even if I have to remove the tranny and the the rear engine cover. It may seem odd, but I get some level of peace of mind that my bus is in excellent mechanical condition and is capable of going 5000 miles, if needed, at a moments notice. I can't ever imagine needing to do that, but IF I needed to, I want it in perfect condition. Ok, I'll settle for 'very good to excellent' condition, 'perfect' might be a bit out of my budget.