Dart tire size? Type???

In that case, very close to stock. It prob has 14" by 4.5" rims. Cross ref the 6.95 and C78-14 tires and you'll probly find 195/75-14 radial for the size. 205 widths in 70 or 75 might be OK or might be pushing it on a 4.5" rim. When you look up the specific tires you'll see the recommended rim widths. Certainly stay within them.
If the car has the 5.5" wide tims, then look at the cross reference for E70-14. I think its 205/70r14.

Considering our roads (and weather) those are good tire sizes for every day use in these parts.
Bigger adds weight.
Taller reduces acceleration but may help highway fuel milage depending on the engine and gearing.
Wider can help traction but the tire compound, road conditions, and other factors play bigger role.