Last week I bought a set of 205/70x15s for my 122 wagon. This was the closest I could find to the original diameter. Actually, they are slightly shorter than the original 6.40x15 tires, but they fit nicely on the stock rims and there are no problems with the body. They actually look like they could have come on the car. Since wagons have the lower rear axle ratio and did not come with an overdrive, the taller tire is needed. I have added an M41 transmission, so the car will go as fast as I have the nerve to drive it (drum brakes all around and no booster).