That's a 30-06 right rear cart stop...don't use it for 308...install the Izzy one which will work on all three calibers. Unless you plan on shooting 30-06 only. My understanding is that the 308 links will hang up on that stop because the 308 round is shorter.
If this is part of a complete parts set, with so many '06 parts, what does your lsp look like where the pawl pin goes thru? Is the belt holding pawl slot wide like an Izzy or is it real narrow for '06 only?
Also, does your belt feed pawl in the top cover have a straight finger in '06 or the curved finger for 308? You can see in the second photo how the finger offsets slightly to the left...an '06 one is straight.
Here's the wide Izzy holding pawl, the '06 is about half that wide.