Ah so it's the 700 or 750 I believe. Mine is the 803 and not compatible if I remember correctly. I have an extra 803 on the ground, I think if you pull the cover on the side of the "transmission" where the shaft meets up there is some sort of 90°output shaft, you may be able to remove the 90° parts and mount the engine sideways, build or have built an adapter of some sort to go from that output shaft, likely spline shafts, to a hub for a sprocket. Then you have the headache of routing some sort of shift linkage around the engine and keeping it functional. I've looked at my extra 803 a few times with similar thoughts.