Wow a question I KNOW the answer to....

While the '66 and '67 buckets look VERY similar in construction they have a few minor differences which make some of the trim different; the back pieces I think are the same, but the side pieces mount in slightly different locations; not sure if this would effect the functionality, but it would not be correct.

Now for the seat tracks - they are TOTALY different. The '66 has fully adjustable tracks you can adjust seat hight, slope (although u had to use a socket); but the '67 were fixed and only had adjustment to go back and forth.

Also the bolt spacing is much closer on a '66 then the '67+

So the seats "should" work but the brackets will not. I think the spacing on the seat side of the bracket is the same, it is just the floor board side; so you could make a bracket to use the '66 upper bracket and a piece of angle iron or bent sheet metal to handle the lower (floor) side.

Good luck.

I can get you pics / dim of both if you need them.