Check out this thread:
https://67-72chevytrucks.com/vboard/...d.php?t=639106
That adapter is getting hard to come by. Last posts in that thread indicate a possible source.
I went to Young’s Gear here in Fairbanks. They didn’t have any new ones but gave me 3-4 used ones and said “try em out. Keep what works best and bring the rest back. No charge.” Great guys, super helpful. That was 3 years ago. Fixed my leak.