Freaky MS box

So how is it not chassis grounded through the mounting hardware ? Are the rubber isolators for both chassis ground and vibration ? Maybe that mounting is like shock absorber mounting ( capable of breaking the chassis ground path ). Shows how much I know/don't know about aftermarket ignition boxes.
If this was April 1st I would suspect the clip end of your tester is on a ALT' or BATT' post, something positive.