Fabricate rear seat left side support rail by riveting gusset HG-1B to top of left bracket HF-73L and HG-1A to bottom. Rivet HG-1A to top of HF-73R and HG-1B to bottom to fabricate right rear seat side rails. Use HM-14 1/8" rivets to secure all gussets.
Fabricate forward (L&R) seat side rails HF-69s as abobe using HG-1A and HG-1B gussets secured with HM-14 rivets.
