We can design a kit to upgrade as much or as little of the system as you wish (or your budget allows).
I completely agree with George that there is nothing wrong with the original hydraulics on the car after removing the stock proportioning valve.
We offer a complete brake upgrade for 15 inch wheels that includes 12.19 inch rotors. Drill, Slotted and Vented with a great looking black e-coating that gets removed immediately upon brake in. This gives a great contrast while providing rust protection on the non-contact areas of the rotors. That kit can be viewed at: http://pantera.saccrestorations.net/sak2001.html
Another option is simply upgrading just the rears. My recommendation is to go with the kit that provides a balanced system designed to work with the stock Pantera Master Cylinder. Our kits are all computer designed and track tested.
Take care, Scott