Given these computers are driving the same system, I would not expect there to be that much of a difference in actual program length. Have you done a file compare to see if there is any coding overlap?

Have have you tried to read the 454 EPROM as a 32 chip and do the chips have standard markings of are they marked with Bosch numbers ? As long as the pin out is the same, you should just get FF FF FF or 00 00 00 in all the tail end fields if you try to read more data from a smaller chip.