Thanks Sycarms, I took the hone to the Robin case last Sunday and no joy on the scored cylinder, it didn't clean up. So this block will need to be bored, to do it right. I'm holding off on investing any money in this lump, I may just part it out, or try to scrounge good used parts, and bore it out. I have my hands on a couple engines, what pans out still remains to be seen, potentially a spicy Kohler CH730 with some parts from Zach Kerber if I can fit it in there, or a Predator 670 harbor freight special, as a backup workhorse.
I have been doing my homework, and it seems the Baja SAE teams have already done a lot of the leg work on the transaxle and CVT stuff, lots of great info out there on these setups. Gears are available should that need changed, but I don't see any need, going by the math provided (attached) from CVTech. Basing my target RPM limit of around 5000RPM (for a stock flywheel) and the high ratio of the CVT being in the .41-.45 range (given the engine can pull it there!) upwards of 40-50MPH is about the practical limit, using even the highest ratio on the H-12 axle being 13.25:1. Lowest gear set is 10.15:1.
FWIW - Spicer has a pretty handy calculator based on ratio:
https://spicerparts.com/calculators/...rpm-calculator