Utility value is key.  As long as it still starts/runs/stops, then it
has some inherent value; just figure out what that value is, and
exploit to suit.  This is what I opted to do with my old rusty '80
Van:

http://users.zhonka.net/zeitgeist/Misc/Grunt%20truck.jpg

AFAIK, it's still hauling organic veggies from the field to the CSA shed.

Casey
Olympia, WA
Biodiesel: "I drive in a persistent vegetative state"
'87 300TD intercooler (212k)
'84 300D (211k)
Gashuffer:
'89 Vanagon Wolfsburg Edition (187K)