I remember in mid to late 70s hearing guys talking of 33s as their vision of large tire gloriousness on Jeeps, Blazers, Bronchos, and other SUVs. I never heard of anything larger back then, but I was in grade school then. So not sure how much I really knew back then.
I just remember growing up dreaming of 33" tires. At that time I had no concept of width. I don't think I even knew there were different widths. I vaguely recall they were all tall and skinny back in the day, but not sure how accurate my memory.
I think it was 33 x 10.5 R15 BFG ATs I dreamed of.
Also, back in the day a 9.5" was on the wide end of normal and considered a flotation tire, a 10.5" was considered a wide flotation tire. I'm not sure if 12.5" existed back then. I think the widest (at that time) was 11.5" on a 35 x 11.5.
I recall 33 x 9.5 R15 and 33 x 10.5 R15 were the big sizes for Jeeps. I recall there was also (on 3/4 ton and 1 ton trucks) 35 x 9.5 R16, 35 x 10.5 R16, and 35 x 11.5 R16 tires. Those are the biggest tires I remember from childhood. I think those were the biggest tires at that time. I don't remember any 12.5" wide tires. I don't think 12.5" wide tires existed yet.
The tall skinny mud tires went through mud very well. I remember that for sure.
Warning: I often edit my posts a few times to get them complete or correct errors.