An option that is not usually discsussed is MECOA (Model Engine Company of America) at
www.mecoa.com. They sell the RJL (formery Kraft) 61
and the HP and HB line of engines. The HP 61 Gold Cup is a beautiful engine. All three are early 70s designs, now made in the USA. Prices are around $190 with muffler, but trade-ins are taken on some models. I had a Kraft 61 on a Super Kaos back in the 70s and it worked well - would have worked even better if I had a lighter touch with the spray gun!
Jeff