It's definitely not from a '67. The shape looks to be a '65, but it could be earlier. Or not even Impala since even Corvair used simiiar seats. We don't have the advantage of seeing the original upholstery.
62 thru 65 buckets are all the same other than the material in the gm line. I would probably leave those in there as I bet you would have trouble finding a set for a 67.
I put 63 impala seat covers on a 65 pontiac I had as I couldnt get the pontiac covers. The fit was perfect and no one ever said anything about them not being correct.
Chrome trim pieces and wood grain veneer pieces differentiated the higher cost Impala and Caprice models from the entry level Biscayne and Bell air. The cars are the same just the different trim and the number of tail lights allow you to tell one from another.
They also added things that you can not see; like sound deadening, and insulation that added weight and value to the car. Which is why the 427 powered Biscuit was considered to be a muscle car, but the 780 pound heavier Impala wasn't. Weight is as important as power when racing.