I noticed that Steven (smbrouss70) had posted in his Blazer build thread about his windshield leaking:
https://67-72chevytrucks.com/vboard/...626978&page=15
I felt bad for him because I love his Blazer and he had to leave it home from a show because of rain. But my understanding is that they were supposed to leak. Why else would they put a drain in the dash?