DaTeacha "As kind of a blast from the past, weren't there a couple of rather well liked old JD models that had just two cylinders?"
Lets see, the A,B,G,H, 40, 50,60, 420,430,520,530,620,630,720,730,820 and 830. there may be a couple more but these are the ones off the top of my head. And even some of these are more popular at times than others. 2 cyl JDs are always popular, but the various models seem to go in and out of vogue.