Is there any information on the rear armrest ashtray lid designs? I understand the 67 version is a larger size. The 68-69 is the same but smaller size. My confusion is with the 68-69 ribbed vs. smooth design. Seems to me I heard a long time back that the originals came as a 3-ribbed design?? Possibly the smooth top was a reproduction and possibly a GM replacement sold at the dealer? Really not much information on these and I suspect there is a lot of misinformation out there on these--