I ran into the same question when I disassembled mine about a month ago and that collar came falling out when I removed the bushing. Here is a pic that shows the collar on the rear arm of passenger side arm - I kept it on the cam bolt so I could remember it. I haven't taken my drivers side off yet so will be interesting to see if it has one also. Somewhere I jotted some info on some research I did on what cars had the collar, If I find it I will chime back. My Cuda is a 318 ac car.
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