By what I have heard and seen from reliable sources, the 65' lightweights in particular were close to or just under the 3200 weight requirements of the sanctioning bodies. So as to not create a protest, weight was cleverly re-introduced into the car by way of extra thick steel plate under the battery tray bolted down in the trunk, extra heavy cast iron side rail differential bumpers mounted over the differential on the longitude rails, an extra heavy cast iron pinion snubber support and of course the Ginormous truck battery. All behind the Center of gravity at the rear of the car.