MP54s were not picked up by very many tourist railroads in spite of many dozens being available when they came out of service. From my days involved in working on these cars I remember some of the items that people in the business thought of as issues with these cars.

More complicated brake systems.
Constant contact outside side bearings.
Heavier.
Extra drag of traction motors.
Unusual couplers

Were any of these items serious issues? How were they overcome? Any other comments?

The Long Island Rail Road used MP54's in two designs during the period of 1908 to 1971. A handful were saved for historic purposes, but sadly, all but one or two deteriorated in teh intervening years, to being almost impossible to salvage. In most cases, water entered the window sills and the corrosion devoured the steel in nothing flat. On top of that, floors dissolved into dust, and the "A" word remains present. While it's true that these were the heart of LIRR's Manhattan life's blood, I would doubt that any will remain preserved in another ten years. If any museum obtains one, it must go in immediate conservation and be kept indoors. I think the only one in reasonable condition remains in upstate New York. A combine may be salvageable at RMLI, otherwise, I thinks they are going to be entirely extinct, and soon.

The Connecticut Electric Rwy. Museum at Warehouse Pt. may have a LIRR version.
I bought the brake handles from the fleet at a Metropolitan Transportation Authority auction. I was supposed to get the controller handles, too, but the employees kept them. The brake handles (with a copy of the auction papers for provenance) can be bought through the Shore Line Trolley Museum's Gift Shop for a $10 (each) donation.