Gravely made skids at one time but now they are hard to find. Here is my version of a set of skids for the Gravely sicklebar mower. They are made with 1/2"x1" flat bar.
Those look almost identical to the worn out (Gravely-made?) originals that came with my sickle. Are the notches sufficient to keep them from rotating? Do you taper the cylindrical spacer where it fits into the original rock guard bolt hole? Have you experimented with longer spacers?
The notches do keep them from rotating. The spacer is a piece of 1/2" black iron pipe, it is not tapered. I haven't tried different length spacers, you would have to have several different size bolts. Sorry Jay, I'm not in the fab business.