Hi everyone. I'm in the midst of slowly putting this 87 back together. In the picture attached can anyone point me in the direction of what seal that would be? That's the only point of leaking I believe and I wanna take care of it

 

That's part of the T-top weather stripping. It continues under the t-top to the back part of the door window. Those look like GM t-tops, so you need the GM set, not the C&C type which is aftermarket.