Hi Craig, answers are inline below...
1. Did you have a ballast resistor before installing this box & distributor? I ask I have two different wires (pink, which connects to the resistor) and yellow which connected directly to the positive side of the coil and back feeds to the other end of the ballast resistor. I know the resistor has to be removed, so I think both the pink and the yellow wires will connect to the red wire from the 6AL-2 box. Both of these wires have battery voltage with the ignition on, but 0V with the ignition off.
Unfortunately, this is for a brand-new install. I started with a repro engine harness, and a completely redone motor with new components. From what I've found the coloring differs all over the place from the original GM schematic...what is a little scary is the yellow wire, I've heard if you leave that connected you can get some back-feed voltage and pop your MSD.
From the sounds of it, I'd actually just go the super simple route (this is what I ended up doing) and know that it'll work "for sure".
Under your dash, the fuse box will have a terminal labeled "IGN". Just run to the hardware store, pick up a female spade end, crimp it on, and run an 18G wire from there to your MSD. It's straight 12V, without the resistor sneaking in there. You could run it through the firewall at the fuse box mating point, or through something like the oil pressure sender hole (where I did). Much simpler, and it's really not a whole lot of work. A little bit of electrical tape, and you can even wrap it in the existing harness to make it look clean and factory.
2. What did the blue wire on your diagram replace? I'm wondering if this is my pink wire mentioned in #1 above.
I think it is. In my harness this was the fabric-wrapped resistor wire (white/blue) that also had that yellow jumper to the starter. As I mentioned above, I just chopped the ends off, wrapped it into the loom, and ran a brand-new 18G from the IGN term to a terminal I installed on the firewall.
3. The brown wire (originally the negative side of the coil) is now connecting to a pink wire on the tach adapter (#8920). Is this your tach signal?
Yes it is. That one was a new run--my engine-side harness never had it, but the under-dash one did.