Sounds like you need a low gear set transmission. Its a lower first and 2nd gear but still 1:1 in drive. Much cheaper option then changing the rear end ratio and/or putting in a OD trans.
a mild stall would help to but you would have to be really careful on your choice as you don't want your curise speed rpm under your stall speed. GM had a factory stall that may be an option. May also want to try calling Continental for their thoughts too.
