Lars, There is a significant range of wheel widths on our cars. I suspect that you have 5.5 or 6 inch rims (measured at the inside of the bead), and in that case 215s or 225s (depending on brand) would be fine. My 71 Comet came with 4.5 inch rims, and that meant that 205s were as wide as you could go. The best thing I can tell you is to take it to your favorite tire dealer, have him look at your rims (maybe dismount one tire), and go by the manufacturers recommendations for rim widths for the given tires, and they do vary a bit by brand. The tire dealer will have charts with all the specs.
Back in the day, white walls were seen on more expensive cars. The black wall were standard and seen a lot on Maverick and Pinto. When I bought my '74 Grabber my friends and I were excited about the wide oval white letter tires seen only on high performance cars. Now white letters only come on trucks and SUVs. I glad they have those BFGoodrich radial TA's.
