1982 Marathon 2 cycle looking for performance mods

[easyrider420]

newbie here, got this thing a couple of years ago with a homemade lift and 22's. 120 psi on the compression check when i bought it. no governor and screams going downhill with a wind but loses most all of it going back uphill. It seems it gets down to its lowest rpm without killing the motor. finally got around to pulling the engine and driven clutch out of it to replace some things like motor mounts tune-up parts and the driven was pretty worn out. I'm needing new ramp buttons and a bushing. Does the foam inside the sheave halves do anything? I've been searching everywhere for a heavier spring for the sheave and haven't found any. I know these older carts are not popular with most aftermarket companies and most of what I've done to it is all custom fabbed. what can i do to the driven clutch and the 2pg engine for better perfomance? Since the motor is out of it I can work on it fairly easily. i like the beefy rear axle. did spicer make a locker for these?(I know wishful thinking!)Thanks for the help in advance if possible