Modern seats in a 67 barracuda
Saw this several years ago, the guy had black leather Volvo seats in his 2nd gen' fish. I say that because I don't recall, fastback notchback, 67,8,9. I didn't get to sit there but man they sure looked comfortable.
Car seats are like furniture in a home ( as in sofa too long for a wall ). We know modern car seats will likely have very short rails. Spacers cure that. Just measure the max width before going hunting. If a seat is too wide you can't get to the controls with the door closed and that sux.
One could spent a heck of a lot more money restoring some of the rotted OEM seats we see for sale here. I often wonder if the guy with Volvo seats knows he has saved enough money to have his OEM rear seat custom covered to match.