We finally removed the wheels of the front of my duster and there are 4 caliper disc brakes in the front. Did this come stock with the 70 duster 340? or is this aftermarket? I need new rotors and pads for sure, the rotors are ground almost all the way through.

Where can I get replacements for this or is there a less expensive way to replace the front brakes? Is it better to go with 1 caliper disc brakes? What size or model number will i need for the rotors?  

no one?  

4 piston calipers were common on 340 A bodies, very good brakes.
I had a 69 Swinger and rebuilt the calipers myself,    Pads & Caliper kits are available from year one.
Rotors without hubs are available from restoration brake Parts, part # BR-2982.