A seat assembly (21) for a vehicle including a seat (22), a seat mounting assembly (20) mounting the seat for movement along an upwardly concaved arcuate path, a backrest assembly (25) having a lower backrest portion (18) coupled for motion with the seat and an upper backrest portion (99) mounted in a vertically extending direction. The backrest assembly further includes a recliner frame and mechanism (32, 33). The seat assembly, also including the steps of mounting the seat (22) for spherically guided movement along said path, mounting the backrest proximate the seat. The assembly (21) and method disclosed further employs mounting the seat (22) having a spherical surface (161) and guide track (28) the guide track mated to spherical support surface (162), and may include slider roller elements (27, 142) such that the seat mounting assembly accommodates lateral, diagonal and fore and aft seat motion (35, 163).