Your guess on the seats is pretty good, they do have that GM 70s vibe.
Also pretty good on the wheel. That style was used on all the GM midsize cars (Chevelle, Tempest, etc.) in the sport packages. The only difference was the horn button as the columns were the same for them all. Don't know if the original Buick wheel was splined the same. These were popular with rodders in the 80s and 90s, but then the muscle restorers took over the demand side of things.