14" rim.....what size tire will work best

Biggest tire option for a stock '66 Barracuda was 695-14. Which you can still get from places like Coker, but they are clse to $200 each. The specs on a 695-14 tire is: 4.30" tread width, 25.3" dia. x 7.00 section width, on a 5"-6" wheel. I don't know if these can be squeezed onto a 4.5" wheel or not. The closest thing in "metric" radial sizes would be 175/80R14, which can be had from manufacturers like Continental, Yokohama,Kumho, Hankook.

Ifyou're in love with 14" wheels, you'd be much better off finding some 14x6 wheels and putting some decent sized tires on the car.