Simplicity was the path, lightness was the goal.  Dual ignition required dual magnetos. 

With one brake on the solid rear axle and the normal brakes on the front they were concerned about brake bias.  They built a mechanical brake bias similar to the one they had on the Mk 1. 

They used an industrial chain.  I think if I were to replicate this car today I would use a motorcycle trans and maybe a cogged belt drive. 

In this shot you can clearly see the twin magneto drive and the cooling fan.  It's really sad that this no longer exists, it would be fun to see how much it weighed.  The smallest Franklin 6 cylinder engine was 335 cubic inches and in the aircraft produced between 125 and 200 horsepower.  A modern 350 cubic inch Franklin engine weighs 297 pounds.  Pretty cool to be less than one pound per cubic inch!