66/7 have hard metal backs and metal trim around the bottom of the lower bun, the adjuster lever pokes out thru a slot in the trim, the 64/5 lever bends under the side of the seat. The tracks are different, the 66/67 has a riser on the tracks to raise them up higher to clear the console a little better. The 64/5 has a cardboard and carpet covered back that screws to the back of the seat, where the cover comes down about 1/3 of the way. Yes, the buns are not as thick as the 66/7, and the width difference as well!
