I knew a guy (not me this time) who pulled a 14x70 MH 100+ miles through the CO mountains with a 1973/1974 K/20 Chevy pickup. Unlike my 73, at least
his pickup had a manual four speed. I dunno what he did for tongue weight - probably some wooden block "overload springs"
He went over "Black Mesa" so he avoided really long steep hills but that's a crooked narrow road so he must have been using both lanes to get around some of those corners.