Hopfully what thay have done is just fit a 6 inch piece on top of the spring.
Main difference is very early ones had a long threaded rod up the inside that joined the top nut to the damper and if it wasn't there or unscrewed from the top nut the sliders fell off if forks lifted too high. Later ones had a reducing plug welded into the bottom of the steel tube and the damper will only come out of the top