Assuming that you want to use a radial tire, you will probably want to use a 205/70 x 14.
I have been running that size on a '66 driver which I have driven over 10K in the past several years.
Honestly, I am considering going with a 215/70, but with the lowered front end on your car, you may experience some front fender interference with this size. It is about 1/2" taller than the 205/70.
Here is a picture, although keep in mind that my trunk is heavily loaded here, so the car is a bit lower in the rear in this particular image.
