The actuator part is really not on the 1-R fork, it is really a cam designed into side cover mechanism that holds the fork.
The side covers are substantially different between the SM319 and the SM326 but they both accomplish the
same function. It really doesn't move the shaft very much to disengage the sun gear when reverse is selected.
Fred


1956 3100 Pickup/Red/350/3sp OD/PS/Disc Brakes
1957 Bel Air Sport Coupe/Red/355/TH350/PS/Disc Brakes
2017 Silverado LT Single Cab SB/Black/5.3/6 Speed Trans
1947 Willys CJ2A w/F-Head engine