Honest to Pete - With 3 & 4 crossed it acted just like the carbs needed syncing. General roughness, low end occasional popping and nothing had a rhythm but it would still drive OK off idle and smoothed out a bit over 1,500 RPM.
I should have suspected crossed wires sooner but I never thought to remove the coil wire to crank it and check the voltage drop. THAT would have found it much sooner.
As I get older, I seem to be forgetting a lot of things I “just did” to quickly trouble shoot things when I was (a lot) younger.
I mentioned this to Alan Merklin but it bears repeating:
”It sucks getting old!”