From what I've been able to gather from numerous posts, there are still some dealers that you can get the orig. GM stuff through. Although it seems to depend on where you are located. When I ordered mine a couple years ago, I was told that there appeared to be 2 sets left in Minneapolis, and all the dealers that mine could link to locally. But I have read of people still finding the parts at the dealer.
I have not yet installed mine, and have nothing to compare against, but I have read that nothing comes close to the GM as far as quality, and you get what you pay for. But speaking from experience with my Camaro, aftermarket seals can be good or bad. I got a set of soffseal for that car, and it worked great for me, where others have had fitment problems.
So, what does it all mean????? I don't know.... I feel fortunate to have been able to acquire some GM stuff. It seems like stuff from other suppliers can go either way.
Good luck in finding a solution that works for you.
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TomS.
*'84 Burgundy T-Type - Mostly stock, mods coming sometime soon
*'70 Camaro - Mostly in pieces....looking for time & $$
*Assorted other vehicles...