GD, I see what you're saying, here is the 09/03 build up till end of production diagram:
And here again is the UP TO 9/03 diagram I posted above:
The difference is in the rod joint #12 needing washers #10 on the old design, and as you can see on the bottom attachment point of the actual shift lever there are 2 of the #10 washers, one on each side.
The 9/03 - onward diagram shows an updated #12 without washers, and no washers on the attachment to the shift lever, only clip #11.
Now, mcurcio as well as Riggo both have the same 6-speed production so I assume that their linkage is identical. Which leads me to believe that either mcurcio has something not engaged properly (could be the fact that he has one original "bitch clip" in place and one that is new, perhaps the original is looser), as well I recommend ALL CONNECTIONS OF METAL TO METAL be lubed up good with grease to keep noise minimal and everything moving smoothly.
I would agree with your theories about a different part GD, if mcurcio was a pre-9/03 production 5 speed. However, since his is same as Riggo's I think we can agree if the issue is in his linkage, it is not due to differences in parts.