What year are their mustangs? that will make a HUGE difference if they are GT's. The old Boxcar style body can HAUL with the 5.0 (if it's driven PROPERLY, and it has a 5 speed) (plus, mods are abundant and cheap for that model... something easily in the reach of a highschooler working a part time job)
I Know it's probably disconcerting Rob, but you really shouldn't listen to them, or race them. You unfortunately don't have alot of HP to put down, and you also have an auto, which bleeds alot of the power.
MOST IMPORTANT, you don't have alot of income, and you CAN'T AFFORD TO RACE. If you break your drivetrain or engine while racing, you are SUPER SOL! Trust me as a friend when I say, without your car, you will go INSANE.
Just tell them that your engine and drivetrain cost as much as their entire car, and you're not stupid enough to risk it. If they present you with $3000 bucks, just to race, then go ahead. (money to cover possible damage to your car; you can RETURN it afterwards)
If they aren't willing to put up cash, then they should shut the F up. If they REALLY want to know what running a top end Mustang against a TOP END 3000GT/Stealth TT is like, then I'm sure we can arrange to have some 3S member show up with a VR4/TT.
MY $.02.
Elton