Hey guys. My '84 BBi, 51723, like a lot of others has had the Marelli AEC104B-660 ignition box replaced with a MSD unit. In fact I'm on my second as the first failed after quite some time. It was an Off-Road unit and is no longer available and was manufactured prior to Holley buying MSD. IMO, MSD products, at least the 6 and 6AL are not what they used to be quality wise (as evidenced by the reviews on Amazon...FWIW). I've done some looking and have found an alternate to the MSD unit. It's the Pertronix Digital HP. I talked to Marvin in Tech at Pertronix, sent him wiring diagrams provided by Adrian at Dinoplex.org ( a wealth of information) and he said the conversion is a slam dunk. The factory coil will work too which is important for originality. The Digital unit, unlike MSD, provides multi-spark through the entire RPM range, is adjustable in duration (?) and the voltage output is also adjustable as well. The RPM limit is adjustable too. I think the adjustable voltage output might be advantageous for the following reason. As some might be aware, the distributor cap on BB's fail often. Especially if they're aftermarket repro's. Tom Meadows at Marelli Service told me that because of heat, and the high concentration of Ionized air in the cap, the cap is subject to considerable stress. When you consider the original Marelli unit only put out one spark per cycle, thus one transfer of spark from the rotor to the cap contact, degradation of the contact surface was "normal". As an aside, Adrian at Dinoplex.org said the Marelli unit put out as much energy as an MSD unit, but obviously only one spark. With the above in mind, if there are multi hi power sparks going across the contact points it would seem to make sense that the surfaces would degrade even faster (if I'm all wet on this let me know...I have thick skin). With the Pertronix unit. Even though there would be multi sparks thru the entire RPM range, if the voltage could be adjusted downward, perhaps that might lessen the wear on the contact points. Lesser voltage but over a longer duration? The price point is very competitive too at about $220. The unit is much more compact than the MSD as well. SO, by chance has anyone out there used one of these units? I think I'm going to make the switch and see how it goes.