Here is what I found from the responces I got. Basicly, I have found that the thick inside door handles started the production and transitioned to the thin (non-ribbed style) handles sometime between Jan 15, 1968 and March 19, 1968. What it means is that I documented car built Jan 15, 68 with thick handles and a car built March 19, 1968 with non-ribbed handles. So far, no one has responded with a car between those dates that has either the thick or non-ribbed style handles. I do have a Feb car that has ribbed handles and I suspect they were replaced (Were they thin style and broken and then replaced or were they simply replaced???). We can speculate on that one. But I have thin style handles documented to the end of production (car #27228). So, it is likely they were used to the very end of production. I would assume there might be some overlap in usage. Hopefully, I will get some more people to chime in. Thanks for all the feedback. I will pass the info on to Rebba Wittington who will incorporate it into the next manual. Thanks, Terry