Restoration of Tom Myl's 1968 Super Stock BO29 Hemi Barracuda

Why black on the under chassis?

I though they were just gunned black in trunk, engine compartment and some cars's jambs (but not always?).

Tom Myl'e told Tony that everything was black except the back seat area and floor that should not be black, it should be reddish primer. Tony did not want to see prime where the rug ends. Thats the only change we did.