I have a 1985 T-10 with the Tahoe package. I am just getting started getting it up to everyday use. When I washed it to see how the paint looked it began to leak inside the rear of the vehicle. I have replaced the front door weatherstripping, but can't find the rear online. I have looked in JC Whitney, LMC and WHolesale GM and I am only seeing generic seals that don't match the one on it or the seal that goes on the tailgate (I already replaced that one).

Any ideas on where I can find it or if it needs to be the one thats on it?