I spent a considerable amount of time reshaping repro fenders to match original headlight buckets. Just before painting the car I found another better set of buckets and they did not match up and had to do it again. I even had to rework the driver side Dynacorn quarter to match up to an original rear fender extension. I had two extensions to work with and both were close, but slightly different. It's a lot of work to make them look nice, but in the end I don't think many people take notice since as you said, with older cars it's not really expected for them to line up perfectly.