The only way to get what you want is to replace the Blizzard1230 with a BlizzardPPC and have a BlizzVision installed. 1024*768 isn't possible with the AGA chip afaik 1280*512 is as far as it'll take you and that is with Superhires Interlace flickering all over the place (there's probably some monitor hacks that change this some but you'll never get some speed out of it at anything but very low color).
