Having the exact same issue with my '96 Tahoe leaking from the top of the barn doors. You end up getting this resolved? If so, which part(s) did the trick?
i bought the LMC kit and added a 3" strip of flat weatherstrip gasket along the "triple joint" where the 2 doors meet in the middle on the top body-side gasket. with the new gaskets i was able to shine light through a gap in this triple joint and the 3" strip of added gasket resolved it completely. took a few tries to get it positioned right.