Thanks, everyone, for the good suggestions.

I will try them all out. I think I have found a good candidate to check the engine out -- someone with more room, tools, and experience.

If I decide to let it go, youse guys will know first.

The engine has about 255K, I assume chain is original.
It did run a little hot after the first change in performance, maybe 10 degrees steady. It blew a steady cloud of black smoke - not usual for this car.