misfiring after losing fight to high speed winds - Spark plug troubleshooting please.

[Dead Parrot]

2nd plug from left in pic, top, looks to have a very narrow gap. Possible that is where your misfire came from. Especially if a piece of carbon lodged in the gap during the fight with the wind.

IMO - 1st step is replace points, cap, wires, and plugs. Worn points can cause a misfire.

2nd thoughts on valve seals. If original, very likely they are worn/cracked from age.

Might be worth it to pull the heads and inspect the valves. Pre 75 heads/valves were setup for leaded fuel. Later heads and valves were a bit different to deal with unleaded fuel.