Looks like an original GT40, or maybe a perfect copy like the Gelscoe cars (or other faithful, exact copies). The seats aren't seats in the conventional sense - the bases are webbing straps which are stretched between welded-in mounting strips:-
The seat backs are glass-reinforced epoxy resin - GRP or fibreglass - which are separate, and retained to the firewall (by Dzus on the original cars, I think?).
@shaunybean on here has re-created them for his build. Pic above is another Gelscoe car, for no other reason than there are plenty of good pics on their website.
@brianstewart re-created a pair for his CCD-chassis build; see on the Build Logs on this forum, and on Pistonheads:-
The upholstery is some form of fire-retardant nylon with minimal padding and the all-important eyelets.
What are you building?