changing device signature in avrdude
You should have, somewhere in your hard drive, a file named
avrdude.conf. My copy of the file has the following lines:

#------------------------------------------------------------
# ATmega2560
#------------------------------------------------------------

part
    id               = "m2560";
    desc             = "ATmega2560";
    signature        = 0x1e 0x98 0x01;
    ...


Try changing the line with signature. Alternatively, you could make a
new entry for your MCU like this:

#------------------------------------------------------------
# ATmega2560V
#------------------------------------------------------------
# Identical to  ATmega2560 but for the signature

part parent "m2560"
    id        = "m2560v";
    desc      = "ATmega2560V";
    signature = 0x1e 0x98 0x03;