lightest a-body??

The lightest A-body was the ’66 Darts that were hand made for the early SCCA sedan class. This predates the Trans-Am, and ran cars based on FIA, or international touring car specifications. These cars were similar to the famous “D” Darts. This allowed the cars to be “designed” by the factory, with each car company determining the accessories, and specifications for the car. The only bug was you needed to run an engine of stock capacity, so the 273 gave way to the 289. Even with that, though, the Dodge won the championship during the first year. The next year, unfortunately Chrysler decided not to compete, and the Mustangs owned the field. The specifications for the early cars were based on FIA homologation papers. The papers for the Dart were not much more than 10 pages long, whereas the Mustang had over 100 pages of allowed changes; that spelled the end of any chance for Mopar.

When the Trans-Am rules from the SCCA came along, it was intended to level the playing field, with all cars not being able to weigh less than 3200 lbs, and all engines at a maximum capacity of 5000 ccs. It wasn’t till the E-body cars that Mopar got back in to it, although somewhat half heartedly.
In 1967, Ron Grable ran a specially prepared ’67 Dart, which was really a remnant of any interest by the factory. This car like the ’66 cars was specially made, with a number of chassis tricks. Unfortunately in order to build a 5000cc engine, it had to be based on the 318, with an early pre LA 318 truck crank which had a shorter stroke. The car also had to run a custom flywheel, as the crank had a different offset, and rear seal from the later engine. Grable’s effort didn’t have factory sponsorship, or the money necessary to make the custom engine parts that would have been necessary. Grable’s '67 car has been more or less “restored,” and is running the vintage circuit, although the current car is running a much more powerful and modern engine based on a 340; an engine that the original car never saw.

The early cars were hand made, and all the panels were acid dipped to the point that the hood would droop if you lifted it in the middle. The cars then could be tuned to set the weight distribution to best favor handling, although the weight of the fully prepared car was around 2600 lbs; give or take.

I know this because I had race cars in the same garage as the Grable effort, and saw the ’66, and ’67 just about every day.