Ron, couple of notes here, EGT's are a tool. you can have high temps and be to rich and you can have low temps and be too lean. Basicly they are only good if you are inside their window of operation. Read your plugs. Your eyes will not lie to you. 10 degrees of chain movement is excessive. you could tag valves on decel at 7k easy. remember that when you decel you have all the valve spring pressure and drag pulling the cam backwards (whip in the chain. that means if you have 10 degrees of crank slack the cam is retarded and the piston chases the exhaust valve closed. At this point your best bet is just to take the head off and post pictures. That will get you the fastest answers to your questions. The rebuild will not be that hard as long as the bore aren't all beat up from being leaned out. Also i am not sure your hauling situation but let me run one by you. I was the last race of the day several years ago. We came off track and had to travel 4 hours home. Car went straight into the enclosed trailer and the doors were closed. Got home had loads of business so i just left everything in the trailer for about a month. Car went into trailer running the best ot ever has. Month later took the whole thing to the track charged batt and drove it out to change the oil and service it...(at track is bad) Anyway after oil change I went out and noticed the engine was smoking and pushing oil into the breather. When I took it apart there was damage to the rings and a couple of broken ring lands. After a complete autopsy we discovered that moisture was the cause of the failure. There was signs of rust in the bores but the gaskets were fine. the real signs were surface rust on the interenals of the engine components. The race oils we use do not have the same moisture inhibitors as street oil and combined with being locked in an oven for a month I am sure that I was the cause of the engine failure. Good luck. Pictures always help

Edit: As far as pistons go I am still a hold out for OE stuff. These days if you want to run a forged piston any of the big manufactures are good. the down side is most of that is custom and this time of year you need 6 to 10 weeks to get them built.