Scott,
Just some info for you that I didn't know, because as I said, I pulled my '72 Fury mirrors off to put a NOS set on. I never thought there was a difference in the C body mirrors, but there is.
After going through a long parts catalog, I was able to find this:
BODY: D POL, MON, C, IMP 72-73 Part: R O/S RECTANGULAR CHROME MIRROR, MATCHES REM CONT ON L. Part #3586853.
So that means for a 72 or 73 Dodge Polara/Monaco or a Chrysler Imperial (same years), you need Part #3586853. It does not list this mirror for a 72/73 Fury, so somehow they were different. Again, I never studied for Dodge C bodies, I just researched back then (about 10 years ago) for 72 Fury. If you want the matching Left remote mirror # it's: 3586845
Using Parts Voice and putting in the number, this is the only hit I got and it's from Collectors Auto Supply. If they do have it, it's NOS and pretty costly (but you'll have to contact them):
Part# Type Price Quantity Description
3586853 NOS $ Call us to check stock and price! D POL, MON, C, IMP 72-73
At least now you know the part numbers of the mirrors and why Fury mirror wasn't lining up.