4.3 liter. Cast iron heads. Crack em a 1/4 turn, blow the recesses out with compressed air and unscrew them from the wheel wells with a long extension on your ratchet. They like AC Delco plugs. I'd be more worried of the secondary ign cables breaking. If they're as old as you say I'd replace them out of hand as well as the cap and rotor. Hope this helps ya.
