Mustang is a Doorslammer which originates from Sydney but was based at my place while on the Victorian show circuit. It is/was an original Boss Mustang until it was 'modified'. I haven't got all the specs on hand but will post them later when I find them.
The sticker on the dash that says "Life begins at 300mph" might give you some indication of its potential.
No, these aren't the cars on the shirt.