1966 Bucket seat cores.

Posting the same details yet again. There are differences between 66 and 67 buckets. Starting at top of seat back... For 66 model, the piece of steel frame underneath the skin is round. For 67 this piece is/was changed to square tubing with holes stamped through for headrest posts. Doesn't sound like much but 66 back frame is about 3/4 inch taller than the 67. The 67 skins fit but not great. Forfeiting majority of the padding on the top helps but it will never look just right.
As far as I know, the 67 model never got the carpeted toe kick at the bottom of the seat back. Remove it and you'll expose a series of holes in the backs where the fasteners are. I suppose one could have that piece of carpet and vinyl edging with fasteners reproduced.
In my opinion, The 67 owner should hold out for actual 67 buckets, hopefully with correct 67 tracks. Good luck to all.