That looks like it, but the end of the pin where the threads are should have holes to accommodate the cotter pin that keeps the nut from backing out. Here's a link to the parts drawing that shows the "slotted nut" as the part numbered 24 in the drawing and the cotter pin numbered 23:lift linkage for 4600
There are also an inner and outer spacer numbered 25 and 26. If you don't mind buying a new pin and spacers then you could use a torch to cut through the end of the lower arm itself and the spacers and center of the pin. Getting it that hot should loosen things up.