here is this for you to make the metal brackets. It should be pretty simple. I didn't round the edges in the drawing but it would be easy to do on a bench grinder
one thing I want to mention is the measurement between the two is shown at .5" that is taking both the block on the one side and the cotter pin on the other and squeezing them as close as possible. So I would say you can have +1/16 to maybe 1/8" in there once you get the block and cotter pin in there.
Do you need me to give you measurements / pictures for the block and cotter pin?
sorry it took so long work is crazy busy right now