In case anyone finds this thread and is looking for info on the third link that goes between the upper mount on the axle to the plow frame near the mule drive slot on the right side only, I had to make one and here is what I came up with. The original is a single piece of 5/8" that is bent into a C shape. I didn't have a length of 5/8" rod so I used a couple of long 5/8" bolts with the head and threads cut off, a length of 1" box tubing, and a spacer. It seems to work OK so far!
Overhead view:

Front view:

I bored two 5/8" holes in the box tubing and inserted the pins I made from the bolts, then ran a bead around the end of the pin as well as a couple of beads between the pin and tubing where I could get to it on the ends.

Here is the spacing between center lines of the pins, 6-1/2":

and, the overall length of the box tubing, 8":

The spacer I made up is about 7/8" long and an inch in diameter, with a 5/8" hole bored through it for the pin:

The box tubing is 1" square:

The pin on the axle end is about 2" long overall:

The pin on the plow end is about 3" long, to accommodate the length of the spacer:

I don't remember the diameter of the holes for the hair pins or cotter pins, but it is not critical, just has to match whatever you are using.
Hope that helps someone out!
Overhead view:
Front view:
I bored two 5/8" holes in the box tubing and inserted the pins I made from the bolts, then ran a bead around the end of the pin as well as a couple of beads between the pin and tubing where I could get to it on the ends.
Here is the spacing between center lines of the pins, 6-1/2":
and, the overall length of the box tubing, 8":
The spacer I made up is about 7/8" long and an inch in diameter, with a 5/8" hole bored through it for the pin:
The box tubing is 1" square:
The pin on the axle end is about 2" long overall:
The pin on the plow end is about 3" long, to accommodate the length of the spacer:
I don't remember the diameter of the holes for the hair pins or cotter pins, but it is not critical, just has to match whatever you are using.
Hope that helps someone out!