Jon,
The pad on my block shows a number of 3836233
I think this is the block casting number and not what red58 was referring to above as the "number off the pad by the distributor".
I have seen references that show that casting code for 1955 Powerglide and 1956 Truck.
As red58 suggested, the engine ID Sequence/Serial number/code is pressed (not cast) into the ledge (pad) to the rear of the distributor. This code included a sequence/serial number and a suffix of letter/letters from 1954 and later which indicated the year. This code will provide good information about when your engine was made.
Tim
