No thanks! In fact there were no 120/80s then, or even 120/90. 4.00 x 18 was the size, K81s won the prize. They came as a 4.10 or a 4.25 - I remember thinking how HUGE the 4.25 looked..
Yes I would have had difficulty getting tyres for a 1098 in 1972 - but you know what I mean!