Here’s what the stock setup on a 1960 looks like. It sounds like your spring may be installed backwards. And yes the slave cylinder pushes the clutch fork toward the rear of the truck. I believe the pull type arrangement was still several decades in the future when these trucks were made.
It sounds like you may also still have air in the lines. In my experience it is sometimes necessary to block the clutch fork from moving (like with a 2x4) to prevent any movement at all during bleeding. This increases line pressure enough to force any remaining air bubbles either out through the slave cylinder or up through the master cylinder. I don’t know why these can be so hard to bleed, but it seems to be a common problem in this application, and blocking the clutch fork usually cures the problem.