What's the smallest tire I can run on 69 Dart?

Hi there,

I'm new to the forum...this is my first post actually. I have recently acquired a 1969 Dodge Dart 4 door. Basically stock with a slant six and "three on the tree" transmission.

I was interested in running some studded tires for the winter here in Eastern Washington and the size of the tires I have are P185/70R14. The car has the 14" on 4" 5 lug stock wheels. The tires on it now are P215/70R14, so I was wondering if I could use a tire (185's) this much smaller in diameter and still be OK with gearing and speedometer accuracy.

Thanks for any input and I will try to post some pictures once I get that part of the forum figured out.