I found them in a NPD Camero Catalog, they are called Firewall to floorpan brackets, The tech there told me they were not for the firebird but they look just like mine, He told me the firebird never had them, Which is funny because Ron (the guy welding the sheet metal) has a 67 and 68 convertible untouched and they are not there. He's had the 68 since he was 16 it was his dads and he's 56 now.

Another Firebird mystery