1966 Plymouth Valiant questions

The rear quarter spears are different on our 2 cars…both are 1966 2-door sedans, one measures 35 1/2” long and the one on the low mileage unrestored car measures 31 1/2” long. Years ago I bought a real nice piece of 66 trim, I cleaned and polished it up and when I went to put it on that’s when I noticed it was shorter…so I’ve seen a few now, I’m not sure why there are 2 different lengths?

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I’m not completely sure either, but I do know that you need the shorter pieces on a convertible, or the trunk lid opens on top of the longer ones and makes a little crease in the trim