....Is this customer service? Am I being unreasonable to expect a part that fits, prompt replacement of one that does not, or a correct part when they send a replacement? A different attitude that shows some concern for their customer?
May not have been as smooth a transaction as you think it should be, but we don't have both sides of the story either.
I don't see how they can account for any and all manufacturing variances and tolerances on a truck that was built over 60 years ago.
If it's only 0.010" (less than the thickness of three pieces of paper) that could be the paint on the dash... If you test fit it before paint, which you should do with all new and probably all used parts too, you could have easily adjusted the fit with a sander.
I think in this case you should have resolved the fit no questions asked, or if you had to say anything a simple notification "hey, this thing was 0.010" oversize, but I made it fit no problem, thought you might want to know for the next guy"
I find that if I, the customer, can be helpful, courteous, and patient, the vendor/service provider will be the same, if not more so.
So yes, I think a different attitude may be helpful.
Grigg