hmm, can't imagine any other way than spot welds - maybe the chrome shop filled some mount holes?
the guards on each side are called 'bumper guards', and the center one is built off a bumper guard, but I've only ever seen a more elaborate center piece like that refered to as a grille guard ... they're all grill guards really, as the function was to prevent the bumper of a vehicle you were pushing from jumping over your bumper and mushing the grill ... push starting used to be pretty common, to avoid those broken arms
Bill