Ok you are doing the right things, changing EA from low to high, my question is what size is the original eprom ???

The 89C51 only has 4Kbytes of eeprom so if the old eprom on the 8031 was bigger than a 2732 which is 32Kbits organised in an 8 x 4 fashion (ie 4Kbytes)then the program above 4K is missing.

Regards,

Kat.