measure the center to center distance all shocks are differant on all models. as long as they are within an inch it wont effect your machine. if you get taller shocks they will lift the sled but keep in mind it will also change the camber on the front skis so that will need to be adjusted.
front shocks should be the same length, I have been useing front hpg shocks from any year on all models, I have not found many different shaft length's on the front HPG's if there is any it is 1/2" at best. You will find the MXZ springs and valveing a little stiffer than summit shocks