I have a 1980 Sportsman van chassis (1981 completion) Winnebago "Minnie Winnie" 20RG RV. It has a 360 and a 727 driving it, but it gets HORRIBLE mileage. I have contemplated engine swaps (4BT, 6BT), but honestly, they won't be cost-effective for the little driving the RV sees. I'd probably drive it more if it got more than the 5-6 mpg it does now... so the thoughts turned to the transmission. The 727 is obviously a non-lockup, non-OD 3-speed. I am looking for the easiest swap to an OD trans, preferably with a lockup convertor. I keep coming back to the 47RH from the 1994-1996 2500/3500 Rams with a TC lockup switch, but I am wondering if there are any other viable and cost-effective options.