I found an aftermarket steering wheel that fits a 3000gt, eclipse, evo. It bolts on with 6 bolts under the horn pad. Is there any aftermarket kits to bolt this to a 66 mustang column?  

You didn't mention the brand of wheel, but I bet if you contact the wheel company they have adapters for their wheels to fit various other models.

If not, it would take the fabrication of a billet hub, splined to accept the steering shaft on one end and drilled and tapped on the other for the wheel, to fit the wheel to the car. It'll be easy for any machine shop with the right info to make the spacer/hub for you (bring them your old wheel and the new wheel so they can measure the splines and bolt pattern respectively...

HTH...
Mark