I found myself in this position not too long ago.  I know exactly what you are going through. Instead of getting a motor, I bought a new 450r that I ended up not really caring too much for and wish I had looked for a motor. Now I'm making monthly payments on something I don't really want, while what I want is in my garage next to it, but my wife won't let me spend any of "our money" on it since I bought the new one. So I ended up parting it out the junked 88' and I'm trying to raise money to get my old 86' 250 back on the trail.  My advice, if this is the four wheeler you want, just find a motor and don't get discouraged if you end up buying crap parts cause $200/mo payments isn't any cheaper.