Riveted the two bearing assemblies together, and drilled the location of each to the firewall. This served to provide the dimensions of the steel tubing that will run horizontally 5 inches from the lower firewall edge. Cut the shaft to length and inserted the threaded inserts and clecoed to the firewall for a test fit. Also cut and drilled the UHMW block that will support the center of the shaft during rotation (Note: Spoke with Van's about the use of UHMW on the (engine side of the) firewall, and they saw no problem with this).