[moneymanager]

I had a lot of trouble with mine initially but it has run well for several years now. I tried first to run with only the optical trigger and could not get a straight answer about whether this could be done with the MSD. Apparently it can, but I ended up adding their box of electronics along with the MSD as I couldn't get the car to run without it. It was all very confusing. Crane first told me I needed their box along with the MSD then told me I didn't!
As to wiring, Crane said connect the three wire molex plug from the sensor in the distributor to XR700 box' molex connector. Three wires then leave the XR700: the red wire goes to an ignition switched terminal at rear which also has the red to/from the MSD. I used a 1.8 ohm ballast resistor so both the MSD & the optical trigger get reduced voltage. It straddled the red line from the Xr700 to the switched 12V source. The black wire is grounded & the yellow wire went to the white wire from the MSD 6. This sounds like what you did minus the XR700 which sounds right.
I was told that I didn't need the ballast resistor but that I should check the heat of the crane electronic box (called the XR-700 then, not sure what it is called now.) Mine was way too hot after 20 minutes so I added the resistor. If you should need a ballast resistor for some reason I don't think you'd find it out in the first few seconds. The heat buildup in my case took several minutes but that's just my experience.
Many people use the optical trigger only with good results. Steve Weiner on this board is one.