This fork is from my 1972 C-8 that was rebuilt. I recently picked up a new 'old style' fork that is like the original fork that came with the scope. I had this drive base changed by Celestron in 1979 due to problems with the RA lock.
I am waiting on a motor to arrive to get the dec fully motorized for guiding. I utilized the counterweight bar weights from my 1980 C-8 to help offset the weight (I may tap the weights to allow threading in the older threaded C-8 counterweights, as imager/diagonal add more top weight.) The C-90 is mounted using a Celestron Precision Slow Motion Adapter for guide star centering.
(Now I need another tripod/wedge