Alright I'm not sure what I'm doing here. My engine builder told me I'm going to need to get an MDS and I bought a used one from a member here. Now what is it for? Where do I want to mount it and how does it get wired up? I could study the website of the manufacturer, but I figured the brain trust here would be a better source of information.

Are you having a six conversion done? Typically used in sixes not fours I do believe. What model MSD you have, is it #6425?
Do you have matching coil?

It's MSD

Is it a 6AL? 6425 is the newer version of the 6420, they hook up the same.
You can find the instructions here.
http://www.msdignition.com/instructiondownload.aspx

Porsche ignition uses a CDI ignition box, the MSD is a aftermaket CDI.

Billy,

MSD stands for multiple spark distribution and modifies your distributor so it shoots multiple sparks per cycle. Really helps combustion and horsepower on the new six you are adding. I have one on the Mustang. The red box gets mounted on the firewall somewhere and then electrical connections to the distributor. You will see the wiring instructions on the instructions. Yes, even we men read instructions, occasionally. You can hide the box but it does not like to be "hot"

I did get the 6AL 6420. Where on the firewall should it be mounted?

Almost anywhere, even in the trunk, the stock six the CDI hung from the front of the battery tray. If you are using FI keep it far away from the FI ECU

Also keep in mind the MSD can be splashed with water but shouldn't get soaked. Don't mount the box on the engine and only the MSD high vibration (epoxy filled) coil can be mounted on the engine. The other MSD coils (oil filled) should be mounted standing upright on something like the firewall etc.

Billy,
You can see the MSD box on the driver side fenderwell. This keeps it dry, ventilated and yet kept the wire runs reasonable.

If I am not mistaken, they also don't like the interference from solid core spark wires we sometimes have. At least that is what the factory says.

I may be wrong, and hopefully someone here possessing far greater knowledge than I will chime in, but I don't think these MSDs add anything advantageous to the 4 cylinders.

This is how I wired up a MSD 6AL on my Type-4. The tach adapter was required for proper tach operation.