aegt5000
I'm not sure. Maybe they are useing the old molds? The only difference looks to be one row of the treads going in the opposite direction. Maybe shoot them an email and see what other sizes if any are offered.
I was looking at the front tires on my 69 since one is split and I was going to change them to some I had gotten from Rick, when I noticed the edge of one tire on the tractor looked slightly different although the treads were identical. When I looked at the sidewall, instead of goodyear, it said tow master.