I had a similar experience with a '67 SDL that shredded the belt on the Interstate. I nursed it to the Rest Area 1/2 mile away, rather than leave it on the shoulder. My wife and I were more comfortable at the Rest Area waiting for the tow truck. It turned out no damage had been done to the engine that continued to run thousands of miles after a new idler pulley and a tensioner.

It may not be as bad as you fear...