Follow up to above...
Dang, looking at a crank, it looks like 1&2 are at TDC at the same time, not 1&4.
Might have slightly belt that intake valve on C2. Will have to do a leak down test but that doesn't explain why it isn't firing on anything but C1.
All plugs show ~5KOhm resistance which matches old ones.
What are the best ways to check for spark and fuel presence?