If you have the bolts and sleeves, here are some possibles. I had the same thing on my 60. The bolt had a locking tab washer. I bought new rubber.
click 1
click 2
I can dig in my files further if you need. Right off hand don't remember a horseshoe plate. I thought the horseshoe rubber fits over the crossmember.
This says 1960-1962 GMC with 305. Seems he is saying 63 up is different. $30 free ship.
This is just a generic pic.