What's the real conundrum for me is that it ran yesterday and now won't start again. If you haven't changed anything other than headlight wire this is a puzzle as to why you don't have spark.
Did you check fuse (fuses)? My 77 and 78 only have 1 - 20 amp fuse, I would guess yours is the same, but don't know for sure.
I haven't looked at the wiring diagrams, but try switching that wire back to the way it was and see if you have spark again. Worth a shot and may be indicative of the fact that there are more issues that need to be sorted in the old H/L bucket. If it will start again, you'll answer that question.
Did you check fuse (fuses)? My 77 and 78 only have 1 - 20 amp fuse, I would guess yours is the same, but don't know for sure.
I haven't looked at the wiring diagrams, but try switching that wire back to the way it was and see if you have spark again. Worth a shot and may be indicative of the fact that there are more issues that need to be sorted in the old H/L bucket. If it will start again, you'll answer that question.