basically the same type of forks I have on the tractor,
I made a frame and on the frame there is a spacer, and on that spacer is a lip with notches that the top "hook" sets on, the notches are about 4 inches apart, (the pin in the top locks in to keep them from sliding, the back of the frame are quick connects on it,
basically copied the same as the top for the bottom but with out the notches, leave some tolerance in them or they will not slide, (to slide my forks I tilt them down and let them hand mostly on the top lip and they will side a lot easier, I will see if I can get a picture here and post it,
by clearance or tolerance, what I mean is look at the pictures of the forks on the top of the slide bar, there setting on the ground and the loader is all the way down, there is about 1/4" of movement up and down if tighter it will make it very hard to move or slide them as they will rack some and lock tight.
I had the old plow and used it frame to make the frame, I would think in a lighter duty loader one could use a heavy wall tubing if you have solid use it, (most all fork lifts have solid frames the forks attaché to),
If you look from the front you will see a notch the width of the fork, it make put them on the frame easy, hook on the top and let swing down and slide side ways. if one try's from the end it is a lot of effort,
sorry not letting me post my pictures for some reason, I will try again