The post GM refers to
http://www.stovebolt.com/bboard/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=4&t=000511&p=
Unless you have a donor for a firewall, the only replacements I found were the Bitchin hot rod style. Your choice for firewall will dictate the toeboard and perhaps floorboards.
If the inner-to-outer cowl panel is at all salvageable, I think you'll be ahead of the game to save the original. I didn't care for the ChevyDuty replacements.