Mine was about twice that when I first started driving. That was with waiting until I was 17 to get my license, a good student discount, a discount for drivers education, and liability only insurance on a 12-year old 4-door car.
Four years later, I'm driving a newer car('04) with a bigger engine, although still four door, with full coverage insurance and have had no accidents or any other moving violations since I got my license. My insurance is still in the neighborhood of $3000 a year.
Based on my own case, I don't think that any 16 year old will be able to get insurance on a Mustang for anywhere close to $1500 a year. The insurance companies look at a young male driving a sports car, and see a huge potential for accidents.
The best thing you can do, though, is have your dad call his insurance agent and get an actual quote, rather than relying on what some random guy on the internet tells you.