What the heck is going on.

[71 super]

Gary, Use method that leon gave you, but let the truck st for a while then crank jack up again and slowly turn from lock to lock. I just completed this swap a couple of weeks ago on my 68 with parts from Randy and while they are used parts if he told you they were right then they are. It does not matter on the drag link as I did not swap mine out or the have I ever swapped out any of the others I have changed over. Try cracking the line coming from the box- return line and let the box free bleed for a short period of time then try lock to lock. The box may have moisture in it from sitting and will take longer to bleed. Another possibility is a) the frame is weak and flexing causing alignment to change with the pump/pulley - had that happen once, or b) the brackets are not tight and flexing at the block or on the pump c) The 68 set of brackets are different than the 69-70 set and the 71-72 set (68 are a pain in the butt to install) and you could have alignment issues.