69-72 c body rotors are not a cheap item - aprox $130 ea and not a lot of choices
73 and later rotors are the same size and are available from $35-$65 each on Rock Auto.
If you can get some worn ones, you can remove the disc from the hub and replace them with some around '75 vintage ramcharger/w100 4wd front rotors (raybestos #7036r, $29ea @ rockauto), you will need new studs too. Hubs may need machining to make it square - the factory would have you fitting them to the hubs and then machining the disc, screw that
I've done that but not with that rotor.
It is very hard to find calipers that exceed the surface area of the 2.75 piston brakes, there are very few out there and unless you -really- need to shed weight, get some, paint em red and feel happy that your factory parts are better on paper than a new set of willwoods
Factory brakes are good and floating calipers are easier to package. However, you can gain brake pad surface area with larger fixed calipers.
