67 bucket seats

The metal back on the 67 upright is nearly full coverage. I don't think that upholstery/skin goes far enough to reach the smaller hard board insert of 68 uprights. My 66 model upright is only about 3/4 inch taller than a 67. The 67 skins just barely fit them. A little spot of hem shows at upper corners of the metal back.
Upholstery shop could put together what you need from 67 and 68 skins.