Not sure if they were the 1st - but my brothers basically started the 4wd class at fairs in our area in 1971-73, can't remember exactly. I remember they had a tough time convincing the sled operator and fair officials to let them hook, and 1st pull was against a 2 motor Hotrod, exhibition pull.

They pulled 1st, hotrod guy went crazy on his pull when he realized he wasn't going to beat their mark.