Missing from the exterior, the hubcaps, rear view mirrors, and the red crown from the trunk lid.
The hubcaps and the crowns were used in multiples for four years straight. The mirrors maybe more of a problem because they were unique to the year but not likely unique to the model. Some of the parts that are there look like they may be pitted which means some effort at repairing them. The biggest obstacle is time, having the patience to find the parts. If you don't have this then you really have no business messing with Imperials let alone this limousine.
Getting into the power plant the engine and transmission are all 1954 and 55' Chrysler, remember that it doesn't have A.C. In that period Chrysler was also producing eight passenger sedans, in each division, that shared the same body as the limo, they may share the same rear end and drive shaft. I think that the biggest problem will be with the Lambert disk brakes and figuring out how to either work with them or replace them with drums if they can't be repaired.