Attached the 633 Control Column Mounts and torqued the bolts. Countersunk for the platenuts on the aft section, and riveted on the platenuts. Riveted on the 904D L and R parts to the aft bulkhead section. Drilled out the 1/4 inch holes for the bolts. Fabricated the center section spacers out of the rigid alum. tube provided. Started trial assembly of the control column and stick bases. Found all the bolts and washers, but saw that the holes for the bolts need to be reamed.