Those mounts fit 55-57 passenger cars, not trucks. Some fabricating would be necessary to fit them to your truck, and no, they don't need to be there if you use the mid-engine mounts and one at the transmission tailshaft housing. The crossmember at the bellhousing area where the original rear mounts fit will need to be modified so the transmission will fit, but don't eliminate it completely- - - -it also braces the rear spring hangers. A search of previous threads on the subject will bring up all sorts of suggestions how to do that.
Jerry
