LMC stuff is junk. classic parts is a bit better but still not long lasting in my experience. Ive used a few different companies for weatherstrip on our old chevys. Best I've found so far to be almost identical to original is Fairchild automotive. Can be bought through rockauto. Any door weatherstrip will be hard at first and will need to be worked in (ie will need to slam doors, rolling up windows will be harder). Ive seen alot of body shops use different weatherstrip on the doors that fit but look nothing like the factory stuff because its easier to install and doesn't need to be worked in but the stuff falls apart so fast and cracks like no tomorrow. And if you need to use glue on any of the weatherstripping you have the wrong stuff. None of the factory stuff is glued. Buying NOS stuff in my mind is a terrible idea. Would you buy a brand new set of 30 yr old tires? Youll be glad after you replaced all that stuff, you'll realize how many whistles and other noise goes away.
I should also mention that Fairchild auto is an ISO 9001 company and is an OEM supplier and has been for over 40 years. They may even have been GM's original supplier. Also they come with a 60 day warranty.