Yes, those brackets would fit. But they're not off a C body either. '78 Charger is a B body.
So, I don't see those brackets working with your C body 11 3/4 x 1.25" rotors. But they'll work fine with a set of B/R body 11 3/4" rotors, which will bolt right onto your '73 up A body spindles. Just get a new set of rotors, use '73+ A/B/E/F/M/J/R spindles and calipers.
In fact, the entire spindle/bracket/rotor/caliper set up off of that '78 Charger should bolt right on as an 11 3/4" swap if you have the rest of the parts.
C-body/truck caliper brackets WILL NOT bolt up to A/B/E/F/M/J/R spindles.
