Company Recommended Size is : 145/70/r12
People use 155/70/r12 size to improve Handling and Ride comfort.
I don't have much experience of Tires, but I had Stock General Radial ST tires. Our Mehran had them for more than 6 years till we got them changed, 2 weeks ago, with Hankook Optimo ME04 ( 155/70/r12 ).
The Hankook tires have somewhat improved the Ride comfort, but on Rough roads the Car is still hard. After all, Tires do absorb shocks but can not replace Suspensions' role.
About the General Tires (145/70/r12), I haven't faced any Handling issue, even in the Rains. The ride was decent if you check the Air pressure Regularly. I should mention that we got our Tires changed after almost 8 Years and still the Tread was in good shape.
Of course you must not Target 8 Years, as 6 years is believed to be Expiry of tires.
Apart from my experience, some people recommend Yokohama S707.