Madbrit and Bill,
Before committing to buy the auto, I would find out what, if any modifications or adaptations will be be required for this type of installation. You may have to lengthen or shorten the driveshaft as well, unless the auto is the same length as the factory tranny. Will another crossmember be required? Tractor transmissions generally weigh in excess of 600 pounds. I suspect the auto may be even heavier. A transmission jack will be required if you make the switch yourself.
onezman
http://onezman.tripod.com/yourrvhaulercom