I believe 175/70 R14 will fit. So will a 185/70 14 and a 185/65 14. The height of the tires are *suppose* to be standardized, but there is some amount of deviation between manufacturers. I'm running 185/65 14 on my '76 MGB. Speedo seems to be accurate still, and the car has tons of grip with these tires /ubbthreads/images/graemlins/grin.gif
I believe the stock tires had a diameter of about 24inches. If you choose a tire size that's within about a half inch of the original diameter you shouldn't have any problems.