I have 4:30 in my DD, 97' Cobra, and they have won me many a street race. They have been a great purchase. Do yourself a favor and get an aluminum drive shaft to go with it. I drive 40 miles one way to work each day and as long as I keep it 70 and under the gas mileage is not that bad. I can get away with a fill up once a week if I don't run around with my foot in it.
Many FWD cars have pretty steep gearing as well. My Audi A6 (AWD) spins at about 3350 at 70 mph. Its not that big of a deal on a high revving engine. I can't imagine a 5.0L mustang cruising at 3350 @ 70mph, but the 4V Cobra does just fine.