A seatback assembly includes an inner carrier module having an upper cross member. The upper cross member includes first and second mounting slots and first and second access apertures disposed therethrough. A seatback frame assembly includes an upper frame member with access apertures disposed therethrough. The inner carrier module is located to a front side of the seatback frame assembly when a locator member of the inner carrier module is received in a locating aperture of the seatback frame assembly. The access apertures of the inner carrier module are aligned with the access apertures of the seatback frame assembly when the two components are coupled together. Guide sleeves are received though the access apertures. A back panel module mounts to a rear side of the seatback frame assembly, wherein upper hook members of the back panel are partially received in the mounting slots of the inner carrier module.