You could search Aminet for hacked monitor drivers. I think there was one which hacked one of the the DblNTSC, DblPAL or Multiscan drivers to a 7xx*5xx resolution which was still visible on a VGA monitor.
I am not sure but I think I remember that there was even a driver hack which was able to display 1024x768 resolution on a multiscan monitor.
Bye,
Thomas
