Best way to rewire for an MSD?

So I've been having trouble getting my stock electronic ignition to run right with my new engine set up so I borrowed a friends MSD unit and it fixed all most of my issues. My question is what's the best way to wire an MSD bypassing the stock wiring harness. When I hook my friends unit I hook the Coil lead to the ballast wire. But I couldn't start the car with the ignition key. I ended up starting from under the hood and car ran fine. I'd like to know the best way to bypass the factory wiring haness, maybe eliminated it completely. Any suggestions?

blue and brown wire at ballast, tie together to feed you small red wire on MSD.

^^Yup^^ Very common if not THE common mistake

Here's how and why

The blue "run" wire IGN1 is ONLY hot with the key in 'run.' It goes DEAD when cranking

The (usually) brown IGN2 is the coil ballast bypass circuit. It is hot in cranking and is the ONLY source of power for the ignition

When you use an ignition that does not use a ballast, you must jumper the two together

I have an old harness with a firewall connectors, I think I'm going to rewire engine section just for the Msd to make it nice and neat.

I have a Street Fire in my car and a 8 gauge stranded wire in the ballast resistor housing.

In order to muddy up the waters, and specifically referring to MSD, you can actually leave the ballast unmolested, and connect the original coil+ wire to the MSD "small red" trigger wire

Why? Why does this work? Won't the ballast drop the voltage? Doesn't the MSD need "full 12 volts?

Here is why. Resistors drop voltage according to CURRENT drawn through them. For example, if you turn the key to "run" on a breaker points vehicle, and measure coil + the voltage will be different depending on "if" the points are open or closed. With points closed, and coil drawing current, the coil + voltage will be anywhere from 6-10V depending on the coil. With the points OPEN the coil voltage will be full battery voltage. this is because there is no current flowing. Your voltmeter doesn't draw enough current to pull down the voltage

The MSD is the same way. The ballast, feeding the small red "trigger" wire of the MSD, does not draw much current. The MAIN power for the MSD is the direct connected big black and big red. The "small red" is like a relay trigger wire. Very low current.

Ohms law. One of the most useful electrical tools on earth

The reason I did this, there was no ignition ballast just the 4 wires that were supposed to go to the ballast jury rigged together. I thought it made the installation look better.

I just ended up making a new harness, and connected directly to the MSD so I eliminated the ballast all together. I'm still using a recurved stock distributor, and high output coil. The car runs great now idles great and there's no loss of spark thoughout the rev range.