Finished up the installation of the firewall insulation today. Rather than use the junky factory plastic retainers, we went with SS hardware: 5/16" buttonheads, rubber-bonded washers on the firewall side, fenderwashers on the insulation side, and nylon-insert locknuts.
We also cut down the bed stand we had used for my 8' F150 bed to fit the 6' C10 bed, then carefully relocated the bed from the back room of the shop to the carport behind the C10.