Scott, you can go ahead and change the oil pan, the oil pump pickup and the water pumps. The blocks are all the same. Only differences are the bolt on accessories.

In '53 the trucks used a center motor mount and two mounts on the bellhousing. That's why you found a plate on the center of the engine. You can pull it off and replace the car pumps with the truck pumps off your old engine.

Numbers on the heads only means right and left and which year upgrade it includes. Not to worry about them. You'll find 8BA and EAB prefixes for ford heads and 8CM and EAC for merc heads. next numbers for both are 6049 and 6050 perhaps followed by a letter or two for improvements.