You say you're dirt poor? Then why do you think you need better brakes? The '99-up cars with their PBR dual piston front calipers and rear disks set ups are more than capable of halting a Mustang with stock size wheels down from any speed.
You would think that, but there were a few times i was driving and had to slam on myt brakes and got a little nervous that I wasn't going to stop in time.
The 99-04 twin piston 10.8" brakes are good for the average driver...but ever since i put my 2-piston 13" Mach 1 kit on....I feel MUCH safer.