What i wonder is, do you want it as light as possible or do you want to make it all around better?
My choise is make it better, then the first thing i would do is change the track to an Challenger Extreme, 162 or 174" depending of use of the sled, then do the runningboards better, preferbly by installing BetterBoards and remove the coolers and install an u-cooler, then i would change seat, better and lighter, install a lw battery and preferbly move it to under the seat or above the footrest.
After this i would consider turbo, definitively.
If you want to proceed, sure you can change skid to an lighter, but better? Especially w.o. turbo, with turbo yes, but i doubt it w.o.
Sure you can change tunnel, lighter and better yes, but expensive.
I like Simmons Gen2, but others hate them, they are superb in real powder, but not as much on harder snow.