Bill, to my knowledge Chev never used a internal resistor coil. When they dropped the external ballast resistor they went to a resistor style wire running from the ignition switch to the coil instead.
As far as running without a resistor for a short test, this should cause no problem.
As some of you know I run a repair shop that specializes in Pre 68 Chevs. I have had numerous cars and trucks come through my shop that had been converted to 12 volts where a dropping resistor was not installed. These were running fine with no points problems. The main thing I see with this is the coil, which has a flat bottom normally, will be bulged out from the extra heat caused by the higher voltage.
I was only recommend hot wiring for a short test only.
