It took me and my hard head a long time to learn the trick of getting a motor to easily sit down on the frame in a 72-93 Dodge pickup! :BangHead: I finally learned that I needed to leave one rubber biscuit loose on the motor mount bracket to get both sides to drop into the holes in the frame, then line the loose one up and drop it down and then tighten the biscuit. That probably applies to any thickness of rubber mounts you use, so hope that helped. :)
