Do they make a larger rear shock for this sled? I would like to have better rear suspension than the stock 8". Do they make a 12 or 14" for these sleds?

An M-10 will work, been used in Polaris sleds for years and available on the aftermarket. Lots of guys have used the early Rev skidframes too. SC-4 I think.

Either way tho it's a fair bit of work and expense.