I recently got and installed a set of Sumi 175/70-13's on my 128. They are listed as "summer performance tires" and replaced the Michelin X's of unknown vintage that came with the car from the PO. I don't intend to drive my car in the snow, so these tires fit my needs perfectly.
First thing noticed: Sumitomo's 175/70-13 sizing is visibly narrower than the Michelin's, with a smaller tread area and more rounded shoulders.
On the road, the ride is smoother - the X's tires were pretty chewed up, with some serious diagonal wipe from (I'm guessing) those crazy 128 rear suspension angles. The car's handling is less abrupt on the new tires, yet retains its speed and relative precision. The nice thing about a 2000 lb vehicle with only 65 hp is that it doesn't need a whole lot of rubber on the ground, compared to a more modern car, and can still be plenty entertaining to drive.
Only time will tell how the new Sumi's wear...frequent rotations will help minimize the effects of that rear suspension. However, based on their reasonable price and availability, these will be my 128 "go to" tire choice for the foreseeable future.
John