Here is my long drawn out story:
Issue #1
I bought the ones for 71-72 and I am assuming they are different because the products in the link say they are for 73-74 but the same logic would likely still apply. The mirrors themselves are nice enough but mine haven't been out in the sun for any length of time yet so I can not comment on durability. My issues started with the gasket sets and screws they provided. They ARE NOT OEM size, sure the holes line up but the base is slightly bigger than the factory and just slightly a different shape. You would never notice by looking at it and I was okay with that myself but when you try and use the gasket they provide with the setup, the gaskets are to small and don't fit properly around the mirror as if they gaskets were made from a different mold. The gaskets are also a hard plastic (not like the rubbery OEM) so your can not stretch or pull them to fit. My original gaskets would not work either since they were not long enough.
Issue #2
The screws they provided with the mirrors are wood type screws (not machined) that are designed to just go into the holes in your metal which would tear it up with out a backing plate. My original screws are not of the best shape anymore so I bought the machine screws on from classic but they they do not fit within the holes (screw bezel & head is way to large) of the aftermarket mirrors nor do they fit in the originals. They are at least the right size to bolt in your backing plate so they at least got the size correct. These screws are a complete waste of money! I knew they looked different in the picture but it looked blown up so I was hoping they might have a smaller head on them. In the end, I just used my originals even if the chrome heading aren't perfect.
Resolution
So how did Classic respond when I sent them pictures of my issues? About how you would expect I guess. Their response was to buy another set of gaskets from their website for $40.00 (which I can not find now so maybe something was done after all) and my response was that does not solve the issue that these are being sold with crappy gaskets and there is no guarantee the new ones will fit either, Especially since they come from the same manufacturer! They told me they do not make the parts, they only source them from OER and they would let OER know of the issue but there was nothing they could do for me unless I just wanted to return them. Thankfully I had ordered a full body gasket kit from Detroit Muscle (awesome company btw) and it happened to come with mirror gaskets. They to were slightly too small but I was able to stretch them just enough to work with the mirrors. Its not perfect but it still looks good and not many would notice. I could still go back and make it better but it was close enough and I scared of scratching my paint at this point. As for the screws, I had not ordered them at the time and since it was $10 bucks it was not worth the hassle of calling them back.
Now you have me worried mine wont function correctly when I get the seats in my car.
Recommendation:
I would return these and find original mirrors that have good mirror glass and have them re-chromed. Like Justin said almost everything aftermarket sucks and your better off reconditioning/restoring original pieces. It may cost more but now that I have gone through the process, more than worth it. I think Justin even said those exact words to me back when I met him a couple years ago and I wish I hadn't been so far into my project that I could have better used his advice. If I ever do this again, that is exactly what I will do!
Sorry for the long response, I just wanted to share my experience. Here are some photos & part numbers of the products I bought so you know not to try those:
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*881239 - 1971-74 Mopar B & E-Body Chrome Bullet Outer Door Mirrors Pair
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MN2882 - 1971-74 B & E Outer Door Mirror Mounting Screw Set