Point of clarification, when you state the 30 amp main fuse is blowing, is it fuse #11 or #2 in the fuse holder? I'm assuming it is #11.
Regarding removing all the fuses then installing them one at a time to track down the grounded circuit... the main fuse is a 30 amp and is in spot #11. It feeds the 30 amp fuse in spot #2 for the ignition switch circuit but tees off before that going to the regulator. It also feeds the 20 amp Engine Management fuse #6 to which I wouldn't worry about since it isn't blowing. The lower amp rated fuses should blow before the main 30 amp so pulling them to track down the ground/shorted circuit shouldn't really help. I would install a 30 amp breaker fuse like Turbo stated and check the wiring going to the regulator, starter solenoid relay, and any other starter switch circuits... Check the wiring diagram.