Steve, save your money. By law you can purchase an extended warranty up until the Original Factory Warranty expires no questions asked. No need to spend good money on something that you can't use for 5Yrs/60,000 miles. Who knows, your truck could get totaled (or whatever) and you wont see a dime of that money back.
If you have already experienced enough issues with your ST that you feel this coverage is needed, the best option might be to trade it for something else. Don't get me wrong, I love my ST but I don't think I would put good money after bad if the vehicle does not proove to be reliable. JMO