If you have the ability to do it yourself, fix the head gasket in the truck. Then sell it and buy a Metro. I commuted to school in a Metro, and it's just what the doctor ordered. Not real comfortable, but reliable, dead simple to work on, and efficient. Just do some homework so you know what to look for when you go shopping. Johnny Mullet's Metro site is a wealth of information.
If you don't feel qualified to do the head gasket yourself, you'll have to balance the repair bill against what you can sell the truck for, to see if it's worth it.
Or you could yank and sell the Ranger's engine, apply that toward a Metro, and save the Ranger's rolling chassis for an electric conversion later.
