David,
Cooper made a 235/75 R 15 called a Trendsetter as of early 2009 and I wouldn't be surprised if it is still in produuction. It has a narrow white wall and they are ok, although after about 5 years the belts start to break down. They are very affordable though. When the tires are replaced be sure the correct valve stems are used. They have a metal elbow, and often the hubcaps will mar the area where the rubber meets the metal resulting in a leak. I have a flat because of that right now. I haven't used other tires on my Eldorado or other Cadillacs for some time, so I can't tell you how they compare as far as road noise.