Good info Tony. Yes, the belt is concerning to me as well. After making some correct measurements it looks like an A-24 belt will fit nice and snug with having to be levered on and the belt touching the top and bottom of the clutch pulley. I'm willing to give it a go. From the info found online the A belts and AX belts are measured the same so an AX-24 it would be. The gearing I have at the moment is 3.20" clutch to 7.00" pulley and 11 tooth to 44 tooth. It didn't seem like adding ten teeth to the rear added much to the ratio in my calculations but I'm just dividing the numbers. Perhaps I'm way off. Was going to at least put the 54 on it but maybe going bigger and just drill an industrial sprocket. My calculations showed roughly 7:1 with the 54 sprocket.
I thought this for ratio. (7" / 3.2") * (54 tooth / 11 tooth) equates to (2.1875) * (4.909....repeating) equals 10.73863636363636
7.096590909090909 this is if added, but it is multiplied to be correct.
So really close to 11:1 ratio on your 26 wheel if that is what I see.
I hope to set up my 20:1 ratio using my 3hp on 26 inch wheel again, currently using 12:1 and get by, just real steep hills doing trail riding it won't do.
You however have what I think is one of those 6.5hp jobs and are probably not going to encounter much problem with 11:1 if going on moderate hills.