I had to do this with mine for about 6 or so years now! Manualy shift it on the column and when towing heavy loads don't use cruise control because you just throwing fuel right out of the exhaust!!
Mines a 94 6.5 buddy basically gave it to me!
It was just a farm welding unit the got on pipeline jobs and industrial sites I keep throwing money at it when it needs it!! Been great to me, and that 29' tow behind is heavy but it did ok against the wind today!!