A car that old that still works is going to have a huge antique value. Eleven thousand won't touch it.
If owning it is necessary, consider a re-purchase agreement. There you buy it for $11,000, and the current owner repurchases it from you for a dollar in a few days.
Your out the $11,000 but you make Grampa happy, maybe. And you can bet there'd be a boatload of restrictions in the agreement about what you could do with car while you owned it.