Miles ?
Efi or carbed ? Carbs doesnt get as good as MPG and cats EFI is bomb . I rode with a guy who had a carbed M7 and we got 2 x the MPG on EFI. Might not have had it dialed but why fiddle when you can pull and go.
M sleds went to a more forward chassis but the K sleds have A arms which are superior to trailing arms. 03 sled from the others mostly have trailing arms . The rev came out then maybe .
If you can rebuild, top ends take guys not much time if you are wrenchy .
900 KK should have all the HP you need for a while.
Beware of the Attak 20 track (dont know if its on that ) . Worst all around track ever . Best powder track , worst everthing else track. Unless you flip it and bend the paddles back using a heat gun and a jig . Even then its not that good .Guys have succeeded , I think all those threads vanished with old Snowest 2 years ago.
A riser only goes so far on Cats unless you want to extend cables on a cat.
A seat there is better spent $300 than a seat ,aftermarket skis = better.