Try ebay or stangparts.com- or just go to a local junckyard.
I have seen a lot of complete "kits" (used parts) for $400. And have done it for less with junk yard parts that I located myself.
Front spindles are best from 94-95 stangs Gt or V6. best price to value to function for front calipers ar post '01 GT.
Rear brakes can be off any 94-03 Gt or V6, but axles should come from a 94-98 only.
93 cobra master is a good choice, but 94-95 Gt or 94-98 V6 work fine too.
Parking brake cables are best purchased from Summit.
I use the 79-86 Mustang brake bias/prop valve and then re-terminated the third brake line off the stock master cylinder to fit the rear port of the bias valve (same as 2300K kit). Don't forget to get the FRPPsolid plug and gut the valve, also run an adjustable prop valve in the rear line, place it in the line at the junction on the passenger side on the firewall.
Also must modify the parking brake handle.
Search the forums and net for instructions or go to FRPP and print the 2300K kit instructions, they now post them in PDF format on their site!