1973 Disc Brake conversion / SBP / 14" narrow steel wheels

you certain of that?
9" front drums would be an oddball for 73, if original. left over parts or someone swapped it in.
I always understood 72 was the last (full) year with 9" front drums available.
73 up was 10" fronts on all A bodies.
Yes, the car is original and has 9" drum brakes. It's a 225 slant, auto Scamp.