You say that the person you bought the car from told you that was the "Wausau Warrior" here is a link with some history on that car.
http://www.cheetahcars.com/miscpicture.htm It was reported to be a Fiberglass Trends car with a custom frame not a Bill Thomas car. Your car is beautiful and the upgrade to disk brakes will be a big help. You might want to go to 8 1/2" x 15" wheels in the rear. Also reinforce the wishbone trailing arms.
The best of luck,
Fred