What about getting some old 68 later dog dish and spot welding to the inside of your 10" caps. Cut the old cap for correct depth if needed. any heat scars on the out side should polish out. Second thought, I dont think it would be easy getting on and off.
You may have wiped a cam lobe. To check the chain slack, remove dist cap, then while rotating engine crank by hand enough to get dist rotor to turn. Once it does go the opposite direction to see how much travel in crank till rotor turns again.
Grab a passer by to tell you when the rotor moves as...
I agree with the above posts, but your engine looks dirty as well. If your oil is getting dirty running the piston through the motions it should cleaned. What is the debris on the deck surface?
I go with the best I can get. Non ethanol If it is available in a 91 or greater octane. If not I use Shell premium first choice, I always run premium top tier fuel and tune ignition advance for best performance.
Little late, but just asked by an 73 Imperial owner how to remove heater core. David, would this be the procedure I should share with him?
I have send him photos from my service manual, but anything I can add will help.
Your padding looks like it has the tar/rubber backing on the jute finer mat. You could use Fat mat or Dana mat type sound deadening and then the dry jute padding on top of that to retain the quiet comfortable interior.