For the longest time, MSD Ignition has sold the old standby 6A and 6AL ignition boxes. These are proven parts long overdue for an upgrade, and finally MSD has seen fit to give them one.
The improvements are not exactly groundbreaking, but they bring these ignition boxes into the 21st century. The new features start on the outside, with a smaller, sleeker actual box that happens to have the same bolt patterns as the old box, making replacement a snap. Inside, the circuitry is all digitally controlled and power output has increased to 530 primary volts and 135 mega joules of spark energy (up from about 110 before).
A big change for the 6AL boxes is the removal of the RPM rev-limiter pills, replaced by a simple dial. The 6AL also now has a plug, as opposed to the old system which had six feet or wiring hanging out. This gives you more control over the wiring setup and makes for a much cleaner engine bay. All totaled, these few small changes end up making a big difference.
Improved 6A and 6AL ignition boxes from MSD
Smaller, sleeker boxes with same bolt pattern
Power output increased to 530 primary volts and 135 mega joules of spark energy