Depends on what you want to do. You can simply get a vacuum module for the distributor. If you want about 20% increase in highway milage, it doesn't take a lot more. That's when you get an advance kit, which has new weights, springs, and an adjustable modulator. You will also need a timing tape, which goes around your harmonic balancer, and allows you to read up to about 45 degrees advance. There was a good article in Chevy Hi Performance magazine about 3 months ago on this.
