I've seen more than 2 varieties on these. Then there are the round edge at the top and straight edge at top in addition to different lengths. I haven't been able to make any sense of the long and short. It would reason that one was for a convertible and the other for coupes/fastbacks, but the rule doesn't always apply to what has been found. On the 65-66 cars, have seen the round edge used on San Jose cars and the other style on Dearborn/Metuchen. Can't say for sure what was being done in 67/8, but at least this gives you some perspective on earlier differences which may have carried over. The master parts catalog does not help, they list a one size fits all. Might check the osborne assembly manual to see if there is a note.
