Bieng the owner of a 56 Smallmouth possibly I can be of some help.
The front apron, there is a chrome grill surround {not the grill it`s self} A chrome strip on the leading edge of the mouth, this assembly is IMPOSSIBLE to obtain. It consists of an upper and lower chrome moulding and two chrome joint covers and the mounting hardware. ALL are N./A.
Things to look for:
The headlight buckets are the three adjuster type {Not the later style two adjuster.}
The windscreen wiper motor is somewhat different in the way the park assembly is configured {although the later style wiper motor will fit and work.}
If the car has an adjustable steering wheel, the circlip that holds the steering wheel on is a N./A. item.
The brake/license plate light, this part is available as a reproduction.
The 56 is a drum brake car and the brake shoes and drums are big $
If the car needs a wireing harness be sure to get the correct one according to the TS # the later style harnesses won`t work!
The park light assemblys {front apron} are somewhat different {flat lenses rather than coned} These are available as aftermarket.} The bulb holders are somewhat different than the later coned style.
Rear differential, this assembly is somewhat different than the later style differential although the later style will fit and work.
Be sure the stanchions and stanchion guides are present as well as the windscreen frame. {I see these from time to time on ebay} {Not Cheap}
The dual mastercylinder is BIG $ for a repro. If there is one present it can be resleeved for just over $200.00
Of course you`ll want to be sure the sheetmetal is in reasonable condition
The gas tank and mounting straps {2EA.} are different than a later model 3a Be sure they are present and accounted for.
The heater defrost ductwork {the metal parts} are N./A.
consists of a 90 degree angle and a Y at the bottom on the heater and the defrost distributors {attached to the bulkhead} {I have seen heater assemblys and heater parts on ebay from time to time}
The side curtains are the wedge type {originals had a one piece plexiglass} not the two piece sliding type.
The 56 has NO exterior door or trunk handles.
The interior door panels are somewhat different, rectangular opening rather than kidney shaped door pockets and a slot for the door opening mechanism. {Avialable as aftermarket}
A 56 has only three lights on the back {two tail/turn and one brake/license plate light}
The rest of a 56 is basically the same as any other sidescreen Tr.
Feel free to message me if you have further questions.
IF you decide NOT to purchase it, I might be interested. Let me know
Thanks