Name that body part. Hahaha

Welcome to FABO.
You'll get better response if you put query in appropriate area.
The rot I see is all what I would consider the cowl. Is it just what is visible or is it bad inside? Not sure what brace you mean...
Lot's of guys on here parting cars. Put it up as a WANTED for either full cowl pieces or sections you want donor metal cut out. If just fixing the holes, I'd probably just use any sheet metal and cut/bend to fit.