Kaptain Krunch, your photo's show the CVT driven mounted backwards to the drive. Whats up with that? I know the buggy world seems ok with that to a point, but I don't think you will get away with that on the larger diameter pulley's.
I was referring to the both pulley's having the fixed sheave on the same side of the belt in the photo's. If that is a P90 it would be a symmetrical system and should have the fixed sheaves on opposite sides. As far as the spring wind I couldn't see it, but it does have a specific wind direction also.
I doubt your going to find a reverse wound spring for a Polaris driven. Also the P90 wouldn't have the dual ramps for Torque Sensing like you see on the go cart stuff.
Its amazing to find out these in there competition stock form will go upwards of 30-40mph with a stock Briggs model 20 back then, even with that firewall. So what kind of ratios does that gearbox even have? Information seems to be lacking on in web unsurprisingly.