Lawnmowerman,
If you are using the rear bracket which bolts to the top of the guard, you are using the wrong type.
For 1960 on, there are two "L" brackets which bolt to the side of the guard.
Regarding the rubber buffers, you will need two 5/16" cycle bolts with lock nuts so you can adjust the height of the buffers.
If you don't fit them, you risk bending your seat base, depending on how heavy you are!
Trev.