Well to be technical that is no 1964 Mustang, it was a 1964 1/2 (or 1965 first full model year).
But running and road worthy the low end is about 9500 dollars, that is for a coupe (not fastback) with a six and no options.
A Mustang rated at a 5 (parts car) has an estimated value of 1100 dollars, again nothing special base model.
A Mustang that can take trophies at a car show goes for about 17500 dollars and a convertible in the same condition can sell for in excess of 30000 dollars.
So that puts the low end at 1100 dollars and the top at 30000 dollars.