11 3/4 brakes

Pics of the setup someone above 'couldn't see working'... ;)

I do need to change the stock MC for one with a larger diameter as the brakepedal-travel is fairly large now.
But that's because the stock '73 front brakecalipers have a 2.597" piston-diameter, and the '73 Chrysler caliper has a 2.752" piston-diameter. More fluid to move.

First off, I initially said it wouldn't work because you incorrectly identified your caliper brackets as being from a C-body, which do have a different bolt pattern.

Now that we know you have B body caliper brackets, I can see how you can run C body rotors and calipers, I just no longer see why. You have the b-body caliper mounts, which are the hardest part to find. You have the '73+ spindles. So, you can straight up bolt on B/R body 11.75" rotors and use A/B/E/F/M/J calipers, all of which would be easier to find parts for.

But, instead you're using bearing collars and spacers to make C body rotors and calipers work. Sure, it'll take a lot more to heat up your rotors, but unless you're doing some SERIOUS racing you wouldn't have any issues with the 1" x 11.75" rotors. And you've added a ton of weight. I suppose it might be a little cheaper if you had the rotors and calipers already, but it just seems like a lot of extra work for pretty much zero benefit to me.