Someone was asking whether the spindles are similar for the AD and Taskforce trucks. I couldn't find the posting, but I have the info.
From 51 to 59, they are identical. I don't know what the difference is on the earlier AD trucks
This is from a Canadian GM parts book
group 6.020 steering knuckle
51-59 half ton forging 3708831 part# 3709756
Bob