The quick changes are still being made. M/T had four of them in Challenger 1, that's some pretty serious history.
They were made for Sprinters and Midgets along with our Dog Clutches. Google Cyclone Racing Equipment on Kustomrama. We're out of Los Angeles-Cook's Machine Works-aka Cyclone Racing Equipment. PM me if you'd like any more info. Thx Scott the PM as well. CK