Hello! I have a 1989 Mercury Grand Marquis. I am have been searching high and low for door gaskets! These parts are discontinued, but does anyone know where I can find these?????

 

This Beauty is a Beast !!

Weatherstripping for your '89 Grand Marquis can be found at "ROCKAUTO.COM".
Go to their "Parts Catalog" -- scroll down to "Weatherstripping".
You should be good to go !!

 

There’s weather stripping for the trunk but not the doors. All the sites I checked are the same way.

 

Eclipse Calipers; Drilled & Slotted Rotors; Police Brake Pads; D.O.T. 4 Brake Fluid.

RockAuto has the weatherstrip -- you just didn't find it. ;>)
Go to "RockAuto.com".
Scroll down to "Trunk Weatherstrip". Click on it.
When the window opens, there will be a yellow stripe on the left side -- "Related Parts".
Click on "Related Parts" -- several different types and shapes of weatherstrip are listed.