Question for those that road race / autocross

you are going to have to make a lot of geometry changes, and likely a complete rear suspension swap. at the front you need to do the shelby mod, oyu lower the upper control arm pivot point one inch, use a 1 or 1 1/8" front sway bar, reinforce the upper arm, and shorten it by one inch, reinforce the lower arm, install a roller bearing in the lower arm, install roller spring perches, install an adjustable strut rod, get rid of the rubber bushing on teh strut rod and replace it with a spherical bearing. you will also need to lower the front end about 1-1.5 inches. at the rear you will need to replace the leaf springs with a torque arm suspension, or a 4 link suspension. i prefer the torque arm. dont forget the panhard bar or watts link. you will need to make room for some fairly large tires, something like a 245/45-17 on all four corners, and dont forget the big disc brakes, 13" in front and 12" in the rear.

you will also need to stiffen the chassis as much as possible, subframe connectors, a center X brace, and perhaps stringers that run from the subframe connectors to the inner rocker panels.

all tha tand even then you might not get close to your goal.

I happen to have both - a '65 Mustang (heavily modified) and an '08 Vette (bone stock outside of brake pads). I track them both at road courses in Michigan throughout the spring, summer and fall.

The '65 is a lot of fun to open-track - raw, primitive and fast. With the right mods (I'm not going to list them - do a search - that's what it's there for), the '65 surprises plenty of other drivers by showing up in their rear-view mirror and passing. After about 3-years of tinkering, the car's pretty well dialed-in and behaves itself on the track. Given my moderate talents as a driver, it turns in pretty respectable and repeatable lap times. It also attracts a lot of attention at the track - people just think it's cool, and I guess it really is.

Having said all that, short of a ground-up racecar rebuild on that old Mustang, it'll never be as fast as the Vette. On the front straight at Grattan, the Vette is fully 10mph faster into the braking zone; about 142mph compared to 132 for the Mustang (that's a huge difference). That's despite a substantial horsepower advantage for the Mustang (Vette LS3 makes 430hp at the flywheel according to GM - Mustang dynoed at 445hp at the rear wheels; I'll leave the math to you).

The first time I took the Vette to the track, I was honestly surprised by how much faster it was than the Mustang; a little disappointing, actually, when you consider how much time, effort and $ are sunk into the Mustang. All I did for the Corvette is plunk down a few bucks at the Chevy dealer. The Vette's behavior is also way more civilized than the Mustang - heck, I don't even bring tools to the track with the Vette, and I've practically got every tool and supply I own stuffed into the Mustang when I track it.

My recommendation, for what it's worth: Build the Mustang for the road course if that strikes your fancy. Enjoy it. Learn how to drive well. Don't get discouraged when stuff breaks and doesn't work right - just try again. If that doesn't work, try again (and again and again). Keep at it, and your '66 will be a very respectable track car that just oozes 'kewl'. Just don't be surprised if you're not giving the Corvette and Viper guys a run for their money...

- Andy

And don't forget that the Mustang aerodynamics is way outdated. Clearly demonstrated by the 10mph difference mentioned above! Things like a front splitter, vent gills in the hood/front fenders, rear diffusor, adjustable rear spoiler will help, but it's still a brick with too tall front, too steep windshield, jumbo driprails, sunken (sp?) windows, lumpy underbody .... But hey, that's what makes it cool compared to a Vette that anyone could buy!
BTW: IMHO a leaf rear can be made to handle. Not sure of the cost/benefit of a gBar or such besides the directly adjustable ride height.