That's interesting. My '82 takes a 5w festoon lamp which I got at autozone.

However, when I looked in my owners manual I see a twist lock "bulb" listed as a 5W/3 cp.

Why not do it the easy way. Take the fixture out, take into auto store, pick up 5w bulb that fits. Or frankly, it might be cheaper to buy from dealer rather than spend hours looking elsewhere.