From an article in Hemmings, re Chrysler Airflows..."The Airflow's body was developed in conjunction with engineers at the Edward G. Budd Manufacturing Co., and Budd eventually supplied many of the Airflow's stampings. To keep production costs in line, Airflows were designed to share many common major components, making parts swapping among cars possible to some degree today. No one is stamping out reproduction body panels for Airflows, so your best bet is to locate the best car you can find or hunt up a parts car.
The flat sections of the Airflow's floors are made of wood, so restorers commonly replace rotted sections with 5/8-inch-thick marine-grade plywood, painted black, Librenjak said. Common areas for body rust include the rocker panels near the running boards, the rear trunk area (on cars with either the inboard or outboard trunk) and, occasionally, the lower cowl where the fenders and doors meet."...Supports Don's reference in post #2