The rubber bushings are already there. its all built in.
make the mount with a round flat plate that sits on top of the mount bush, Depending on the size of the center hole and how you want to do it, Either a long bolt up the center into a nut welded to the top plate, Or, A long welded stud hanging down with a threaded end to wind a nut onto (Much better) It might have a taper on it, But anyone with a lathe could easily make the stud for you, then just weld it to the chassis.
Mount it all to the leaf cross member, then fill in the blanks between the mount and the front crossmember. Could even make it look real pretty if you incorporated some dimple dye holes into the sides of the mounts or something