Those 215/75/15s are pretty close to the 6.70-15 tire that was common back then. Should be ok on the 7" wheel, though you may consider a 235/75/15 as well. It's a little wider and taller, and will be a better fit for a 7" wheel. Air them up to around 35 up front, maybe 35-41 in the back depending on what range you get (P rated. P XL, or LT C range), it'll still steer fine. I'm running even wider tires, 30x9.50x15, with manual steering, and have no problems turning.
