The back side of those weld-in nuts aren't really accessible (unless the cowl is rusted away like mine were.
But even if you can't get to the back side of the nuts, soak them well with your favorite penetrating oil. If you aren't worried about paint damage, you can try heating the bolts with an OA torch, which usually breaks them free. Then another dose of penetrating oil and they should come out.
Good Luck
