Lower gears will spin less out of the hole. You need some 8 inch wide tires or 9's if they will fit. Once it starts to try and hook you'll probably also get spring wrap up so some slapper bars or overrides/underrides will help that. If you keep burning down the tires with your open track you'll wind up breaking a spider gear in the rear end. They are especially prone to that if you start spinning on grass or dirt and then get up on the asphalt. If you still have a little hesitation on initial launch try going a notch closer to the carb on your pump shot lever. More initial timing can also help a launch stumble.
You can see my 65 fastback at: http://hottarod.stangnet.com/
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You can see my 65 fastback at: http://hottarod.stangnet.com/
http://members.aol.com/macstang/Gifs/macstang3.jpg