This needs a rethink and is unrelated to his overheating issue.
I never change multiple things at a time when trying to isolate the cause.
The timing, that's something that strikes me. "-5 at idle and dwell of 43"...So What's the power timing?
OP , set the total timing to 32-34 degrees@full advance and or +5 btdc to +10 btdc @idle then test drive it.
And make sure the exhaust heat stove flapper is not stuck closed!
