As Percy found out, the ones from Mr. Fiat are too thick at the bracket ends. If they are used without the rectangular plates, the spacer that goes inside the hole in the rubber hanger is too short, which won't allow the bolt to reach its proper torque without severely crushing (deforming) the rubber and bending the u-bracket.
The simple solution for these rubber hangers is to trim the thick ends with a bandsaw so that the entire hanger is the same thickness.
John