If you insist on keeping the car 100% stock, then wax the hell out of it and PARK IT. Put it in a garage with a fancy floor, a lot of Buick pictures on the wall, bunch of lighting, and some nice lounge chairs around it.
If you want to drive the car and not replace head gaskets, there's a laundry list of preventative maintenance items that HAVE to be taken care of, and a few parts that HAVE to be replaced just do to age. With out taking car of all the necessary stuff 100% first and some monitoring equipment, you WILL come to a fork in the road. The left fork is a head gasket job (if you're lucky), the right fork is selling the car in a basket because you're spent all your money on the car and you're sick of it.