Reset two of the firewall bottom rivets. Match drilled forward bulkheads to center section. Match drilled aft bulkheads, seat ramp supports and aft floor support angles to center section. Deburred and countersunk all parts. Primed all parts. Installed 12 bolts to forward center section. Riveted 4 nutplates to forward bulkhead subassembly. Riveted 2 nutplates to L forward bulkhead. Riveted both center section forward bulkheads to subassembly.