Basic mechanic Q o' the day: install hub dust caps - ever had one that was hard to seat properly?

As long as I've owned my Dart, I've had one ugly hub dust cap that was dented by a previous owner who evidentially used a large rock to get the cap in place at some point in the distant past. It did the job of keeping dust out, didn't leak any grease and I always had wheels that hid them so I didn't really care...until now.

Sure enough, Rock Auto had them in stock for a few bucks. They had the domed same shape as the stock pieces so I ordered them up.

I've never had a problem getting these in place...but this one just isn't cooperating! Typically, I have been able to line them up by hand, gently tap with a rubber mallet to get them seated, then I could tap them right in and they would go in without a second thought. With these new pieces, it appears that they have precisely the same OD as the ID on the hub! :D

I spent a few minutes with some sand paper to try to take off a tiny bit of material and bevel the edge a bit but so far this hasn't helped. Before I get too aggressive with it, I just wanted to check with you guys as to whether or not there might be a trick...and that perhaps when dealing with a cap that hasn't been on and off of a car for 45 years, if the tolerances might be a bit tighter?

Thanks for any tips!

dented cap.JPG