use a 3 or 5hp Briggs with a mini-bike style torque converter driving the transmission,might have to re-package the engine/trans together down lower to make it work out..I'd make a subframe to sling both underneath the center.I'd think as long as you have about 3"clearance or so it would work out OK. I could look at that roller all day just in its present shape..it's kinda inspiring!!