Ames and Classic Ind have the shift lever/plate slider seal (these are plastic). Neither carry the 4 rubber seals. The IPC shows the slider seal #9 and 2 other seals #s 15 and 16. http://www.tpocr.com/68-69fbconsoleipc.html
Does anyone with a 68-69 with AT have the 4 rubber seals on their shift plate or is it just for Camaro?
Those rubber pieces don't look like the two rubber pieces that are shown in the link you posted #15,16. My guess would be , the 4 rubber pieces are for the Camaro Horseshoe style shifter. I have not seen them pieces on my 69 shifter, unless the 68's are different.
Also, not sure when they came out with the style of shifter that you can push to the side as you up shift to only go up one gear at a time, my 69 shifter is like that. It takes a different slide seal, it has an oval hole in the middle to allow the shifter to move to the side. Just in case your shifter is like that.