I'm using a Classic Industries hood tach with an Ignitor II. There is no problem with this combination. I don't know about the MSD 6AL.

The installation of the Ignitor II was not difficult. I had the distributor out, but you could do it in the car.

I previously had an Ignitor and fried it by hooking up the wires to the coil backwards after 4 years of trouble free use. Oops.

To get 12 volts to the coil, I replaced the black wire with the purple stripe on it that goes from the bulkhead connector to the coil. This is the calibrated resistance wire. The wire I replaced it with was just a regular wire. Bada bing 12v.