Craig,
You are right, I have been flooded with people wanting to know if and when I can make them one for their cars. Unfortunately my day to day workloads are already very high and after hours I am occupied with Australian rally championship car preperations and of course my own 1200 coupe rally car. I competed on the weekend and broke my option1 straight cut gearset so I am very busy trying to redesign bits and pieces for that.
I am not going to make a heap of these spring loaded lockers because I designed and built mine to suit my H165 centre after it's internals were modified to accept the plates etc. I know from experience the better they are "fitted" to the centre the better and smoother they work. I would need your diff centre as a starting point if I were to make one for a customer because I wont accept manufacturing something if I cant guarantee it's effectivness and the final dimensions will depend on how much work needs to be done to your standard open centre before it is measured for the new plates.
I have given A14force (1200 member) a lot of info re how to manufacture the spring loaded locker and he said he's going to have one made up. Should be interesting to hear any feedback from him because his application will not be rally but drag.

Paul.