Huh, I have a brand new pair of those Metro Seals for the Doors still in the box and was so discouraged from the roof rails I ordered to OEM ones (which aren't that bad compared to the Roof Rail Seals).
Guess maybe I should try an sell them.
Anywho, from what I've been reading through the threads here and over on Turbobuicks the aftermarket Door Seals seem to work out fine but again it's hit or miss with the Roof Rails.
I don't think there will ever be a definitive answer one way or the other. The people I spoke with over at oldbuickparts where I got mine said they've sold literally 100's of those RR Seals and gotten no complaints about fitments.
To tell you the frank truth NOS when it comes to rubber isn't all what it's cracked up to be, least in my case.
On my Regal both the Drivers Roof Rail Seal and the Dew Sweep for the Door Glass were replaced back in 2000 (I was able to order the stuff from the Dealership back then). Neither lasted more than 4 years before they started cracking.
MoRbiD