550 will work. It's exactly the same. I've seen these in C bodys. But, I dont wanna burst your bubble, but I have a used bulb in my stach & I won't sell it. These are unbearable to find. Back in the 80's I discovered the C body's had these sane lights, so I made a quest to hit every junkyard within 100 miles of my home & buy every dome light, busted or not. I have well over 75 of them, most were complete. I sold some, but today I have 2 left. They are not the best, but bulbs were not always with them. Living with my parents at 21 years old, they didn't care about my car stuff. I'm in Wisconsin, so right now if I wanted to go look for one, I'd be crazy, cause there are none anywhere, because there are NO older cars left anywhere. Sorry, but I will say, watch swapmeets, an occasional C body done light turns up. Check it fir a bulb and buy it. That's my best advise.