Not sure what size pulley is on your saw, but I hope you figured the ratio. Years ago, me and a buddy of mine hooked his 830 John Deere, the largest and last of the 2 cylinder line, to his buzz saw. I'm not sure how big the belt pulley was on the old J.D., but the one on the saw was approx. 4". At an idle, the saw blade was actually whistling!! Sounded like wind through the trees..!! We shut it down, and decided to put my little BN Farmall back on.
Do you have a Rockford clutch on the engine..??
Might be a thought to keep your eyes peeled for an old hammermill setting around. I have an old Montgomery Ward I still use. It is a cast pulley, approx. 4" dia. and approx. 8" wide. Not sure of the shaft size, but sounds close to that.
Even at a 1 to 1 ratio, if you keep the rpm's up to keep decent oil pressure, it should be turning plenty fast to cut wood..