The cap and rotor on these cars doesn't often go bad but the PIP in the distributor does. Pull the cap off the dizzy and look in there. If you see a silvery powder in there the pickup is likely toast and a new distributor is your solution. Unless you have a shop press, then you can replace the PIP itself.
2000 Mustang GT Steeda #0048 34k miles. 99 Cobra 4V swapped, FTBR IRS swapped, exhaust, tuned by James Gordon.
Just because I give you advice, doesn't mean I know more than you. Its just means I've done more stupid ****.