I also have an 81, #311, and installed a windward sheeting car last year. I used a Model 1575 Mid-Range car, Model 1511 Hi-Beam Track with end trim caps, and 1516 Mid-Range Traveler controls to set it up with a 4:1 ratio (all Harken). The Hi-Beam track uses bolts slides so you can match your existing bolts holes. I can't remember exactly but you use only seven bolts or so, far less than the original installation. The other thing you'll need to do is raise the track approximately 1/2" to provide adequate clearance for the travreler car. I used a 1/2" thick piece of Starboard plastic (you could use a piece of teak) under the Hi-Beam track. Not only did it raise the track it covered the unused holes. One final item, I used a continuous traveler line of 3/8" Sta-Set attaching each end to the traveler controls. You need about approximately 30'. There is a good article by Rob Van Name on the Class web site, it further explains the process. Hope this info helps!!
