3 speed key lock-out

Having owned a real early 70 340 4 sd Duster that didn't have this function. I can tell you first hand why it is there. I blew a clutch/flywheel and when I reached up and turned the key off to kill the engine, it locked the steering wheel and I then ran off the road into a deep ditch! Later on in 70 they added that feature. I'm fairly certain there was a rod that ran off the reverse lever on the trans to a lever on the column that turned the collar on the steering column which in turn allowed you to turn the key to the lock position and remove the key.