65 coronet wiring issues

Correct. All 1965 cars had the same bulkhead connector, with the big "bus bar" feed-thrus for the thick ALT (A1) and BATT+ (R6) wires. That is why I put one from a 65 Fury in my 64 Valiant (enlarged cut-out 1/8"). C-bodies had an additional bulkhead feed-thru (4-pin, I recall), forgot what for (wipers?). Don't know if B-bodies did.

Most likely you have a disconnect in the IGN feed, plus the headlamp circuit is touching the IGN circuit. Often things like that happen from melted terminals in the bulkhead connector, but could be in the fuse box too. The fused (semi-welded) ACC junction in the under-dash harness is also a corrosion concern, Don't recall if C-bodies have that, but probably do.