How much does a new Mustang GT weigh and if any of you have a full roll cage how much doe it weigh with that.

 

According to consumer reports a 2006 mustang GT coupe with MT has a curb weight of 3,590.

According to cars.com a 2006 GT premium coupe weights 3,483.

so i'm guessing the correct answer lies somewhere around 3,400 - 3,600.

 

My ragtop weighed in at 3670 (less than 1/8 tank gas - no driver) at the track before adding the 6-point rollcage.
The chrome-moly cage I had installed added about 60 pounds to the car.

 

That must be a pretty darn accurate scale at your track, as Ford lists the weight of the 2007 Mustang GT Premium Convertible
at 3612 pounds. They obviously don't weigh the car with any fluids in it, so the fact you had only a couple gallons of
gas and other fluids would make up that additional 58 pounds.
The convertible weighs like 150 pounds more than the coupe.