Mopar Muscle Association UK

This is the difference between the 73 E body 10.98 size disc (left) and the Cordoba B 11.75 disc (right)...
had the drilling and slotting done for better dust clearance and appearance
and with the Viper calipers and prop valve adjusted right should make a reasonable difference.

Late 73 on A body disc spindles rarer than rockin horse manure
79 Cordoba discs
Viper ali 4 pot calipers
Goodridge braided flexi lines
Wilwood prop valve
should all go under a 15" wheel
shall be able to tell soon

Cos you're using decent calipers,pads, braided lines etc it should all work fine using either size rotor, doubt it makes much difference really.
Cool looking system Steve, be interesting to see how effective it is

Little bit more leverage with the bigger disc but probably minimal

but newer system must be good bigger choice of pads, lighter, quite a bit .. etc

Not convinced Viper callipers will fit with 15" wheels but if they say they do then they probably do.

Don't forget that you need a 2:1 pad area difference between front and rear brakes. Otherwise brake bias will be well off. Not sure how that works with drums on the rear. But my stock 11 inch HD drums were WAY too big for the front discs and I had to reduce the line pressure to the drums dramatically to get the bias right.

Viper Calipers DO fit 15" Wheels.

The Sox & Martin Barracuda had them with ARE's; and I also fitted them to a Charger with 15" Steel wheels...

Got a prop valve and 7/8 rear cylinders