340 Tach Drve Electronic Distributor Question.....

bradfields, msd has a fairly new box that takes over control of your ignition. It allows you to lock out the advance and digitally control it.
It is the shiznit and you can hide it under your dash!

http://www.jegs.com/i/MSD-Ignition/121/6530/10002/-1

Following the introduction of the 6AL-2, there will also be a 21st century version - a laptop programmable 6AL!

This advanced ignition control provides street and performance cars to take advantage of tuning in an ignition curve or boost timing map from a PC. Also, using MSD's Pro-Data+ software will provide simple adjustments to a two step rev limiter, step retard and more!

All new housing, digital circuits and performance
Built-in 2-Step rev control - with rotary dials
Higher output with up to 135mJ and 535 volts
Accepts Hall-effect, points and mag pickup triggers
Managed by an efficient digital controller