from back in my AHRMA days.....
parts unlimited catalog sold a basic piston dampner in three (maybe 4) different lengths. I didn't even have to shim my steering stops!
a clamp was also available in all the popular 70's fork diameters
overall it was super easy to mount and sorta remember it was cheaper than a set of race tyres...you know, tires made by Avon
I would venture to guess that no radiators = easy universal install, while the presence of radiators require 'model specific' hardware
Mark