Throwing around a couple dangerous ideas!

Those cars were good cruisers as born, they don't need much to do well in this present century, just simple upgrades and modern tires.
For a lil pep consider supercharging; turbos are a wonderful addition to a fresh smogger-teen, and won't destroy the car.Plus you can run hi-way gears and lo-stalls, for a nice comfortable cruise, while roasting the tires at will.