Not to me. # 1 and #6 do not look normal. Something going on in those holes. Burnt valves high on the list of suspects IMO. A leak down test would reveal that. Buy a tester, best tool I ever bought as far as diagnostic.
I don't believe it is abnormal for a slant six to have cylinders 1&6 running richer than the others... some intake manifolds were significantly worse in this regard than others... and 1974 was not one of the good ones...
Yeah the plugs are not great, but they are not the issue...they are just reporting a rich condition, and this was discussed last week or so...
I'm thinking a vacuum gauge will tell us more... and maybe a better carb than the 1945 Holley carb from the same year will solve all of the problems? I have a 1945 and I have futzed with it plenty. I look forward to the day I put a better carb on, tho the 1945 I have is a truck carb, and a few years later.. so not quite as bad as the early 70's stuff.