The basic unit for the Langdon's small diameter HEI is a 2.8 Liter Chevy V6 distributor with a modified housing and shaft, and a drive gear that's compatible with the stovebolt six camshaft. There were only a few years of production of that distributor with vacuum advance. I made one from an offshore clone of that distributor, and installed GM original equipment electronic parts. I doubt if I'll bother doing another one, as it's a lot of work.
Pertronix comes in two types-- - - -the ones that have had a catastrophic failure, and the ones that are going to. Leaving the ignition switch on accidentally without the engine running will fry one in a matter of minutes, just like a set of points.
Jerry
