smpcp

Follow Ferdman's advice on the PPI.. a must do.. Also, I 'd do a carfax to see how many owners have shared (or skipped) the maintenance! Cheap price for peace of mind.
Maybe you are getting the real deal, maybe not. Those odometers are easy to change or replace. They will break too! (Mine broke about a year ago. Had it replaced by an indy)
Did you check the appearance of the engine compartment? (Should still be reasonably clean.) Or the wheel wells ( should still have a good paint surface)? If the steering wheel is "soft" to the grip that may indicate more use than 55,000.

My 88 had a small leak in the head gasket, which was changed before I bought it (in 2001 w/41,000 miles).
The valve seals had to be replaced at 55,000 when it started guzzling oil (qt every 500 miles): $400.00. Problem solved. My guess is the seals dried out with time.

I am at 83,500 now after 4 1/2 years. I think the only other thing that's been replaced (other than tires) in that time is the flex coupling. Still has the original exhaust 18 years later.)

I don't think 5,500 is a bad price for the car, depending on how badly damaged and how well it was repaired & repainted. If I was going to sell mine, I'd ask about 7-8,000.

No,your'e not gonna keep up with that blonde honey in her mustang pulling away from a red light, but when you eventually pass her, you're riding in much more style.

All that said, your'e on the right track in looking for a 300ce IMO. Timeless looks and styling. A $55,000 car for $5,500. Such a bargain!