Darryl,
The stop collar actually performs 2 tasks. Firstly, it controls the load on the shock absorber spring, and secondly, it acts as a stop for the lift of the shock absorber cam. Without stripping one out, I can't give you definate dimensions, but as a guide, the diameter needs to be about the same as the diameter of the boss on the cam, and the thickness about 1/2" to 9/16". If you dont have the original spring you may need to experiment with the thickness of the stop to get the correct action - maybe, start off with a 1/4" thick stop and several 1/2" washers, and adjust the thickness to suit. On the standard set up, it was possible, under hard acceleration in the lower gears, to make the shock absorber want to ride over the top - hence the large OD of the stop. When complete, the through bolt and nut should be fully tightened to prevent wear on the drive dog (the castle nut and split pin are not there for adjustment)
Hope this helps,
Eddie.
