I have a 2001 zr 600 efi le, I would like to go to a 136"x2" track.
My question is:
What parts will need to be changed?

obviously the rails, and rear springs.

will my chain case work with the 2"?

I thought about slipping in a new mountain cat tunnel w/ wide boards.

TIA

Some people just add rail extension brackets to make their short track a long. The sliders don't go back as far as they would with a factory longtrack but it doesn't seem to matter. You will need a tunnel extension to cover the extra track. Your chaincase will be fine but I think you will need smaller drivers and possibly a regear for the 2 inch.

How does your twin turbo mustang go? I am a huge mustang head.

http://www.geocities.com/fordguru69/Mach1Muscle.html