are you planning to drop the mxz arms etc onto the summit rails? (cause that definitly won't work with the acm on rear arm) if you're planning a straight swap it may work for you... i believe the older rails were extended at the back behind the rear arms.
i'd check the distances from the lower front arm pivots to the rail tips,the lengths of the front arms,and the length difference from the front arm pivots to the rear axles before getting too carried away.
if the front is all the same and the rear mounting point works without major relocation it should work...BUT!...the length difference on the back might not leave you with the track length you're looking for depending on the amount of set back the original machine had for the whole rear skid :face-icon-small-sad (some of the older sleds had @ 10" c/c from the drive axle to the top front arm mounts...around '02 they moved it back to @ 13" c/c for a better approach angle w/shorter rails to run the same track length).
you may have to play around with this distance to get the "right" length- but if you move it too far you will have more issues (like lack of weight transfer or rails poking thru the track windows...:face-icon-small-sho )
another thing to watch for is the length of the rear cooler...going from 121 to 136+? may leave you with some cooling issues that may or may not be cureable w/scratchers because the cooler might not run back far enough for the snow to be thrown against it by the new rear axle location:face-icon-small-sho
if all the measurements work out and you have the 10"ish setback dimension- you might entertain the thought of sliding the skid back to the 13"ish position -it's a whole lotta work thanks to the steel rivets on the back mounts though...
