It's a fairly rare setup. I've only seen one in person. That 4th rod is a staging rod used on 3 speed versions only without a console. Not for factory 83/84
Hurst/Olds applications, although 88hurstolds was working on a custom cross pin to add a 4th rod to the 4-speed setup. You can get back to reverse quickly with it instead of wasting time fiddling with all the rods. I've never had one or used one, so I can only go by what people says it does.
As explained to me, when you pull all the rods back, you're in 1st gear. Do your burnout to clean/heat the tires or slicks, then use that 4th rod to get you from 1st back into reverse. Back up, drop the rod back all the way again, and you're instantly back into 1st gear. The cross bar/pivot pin is attached to the transmission gear selector. The pin has holes in it that are clocked to allow you to push the button on the shifter down, and when you do that, a spring loaded pin is pushed into the cross bar. As long as the button is pressed and allows the pin to line up with the hole in the cross bar in the allowable sequence, you can move the transmission the gear you wish with the levers.
