If it were me, I would get a 141 skid out of a M. Put a couple spacers in the tubes for mounting and figure the hole placement out when installing the track. Pull the skid back with a ratchet strap and fabricat whatever I need for a rear mount. He will also need a tunnel extention. I don't think a old mountain cat skid would just bolt right up in a ZR either, the ZR is only 121" and the pivot point should be a lot farther ahead than a 144 skid. They used to change some of the MC's skid's to the ZR position to get a lot more transfer. It involved moving the mounting holes ahead on the rear of the skid frame. The M skid is a lot lighter and transfers much better. You can usually pick the complete skid up for $300 to $350