If side-curtain airbags in seats are not mandatory, and I don't think they are, seat manufacturing in-house should be fairly straight forward. Frame, foam, cover, mount it to the truck. Funnily enough there's a manufacturing facility right by me that makes custom seats and upholstery for aircraft and it's a fairly small footprint for the volume they allegedly produce. Should be able to fit that right in with the rest of the factory if they outsource the frames.