Aloha Norman,
I feel your frustration as I had a similar problem installing a 123 ignition on my 250 SL two years ago
. I had decided to upgarde to an electronic ignition at that time for the improved reliability and simpler maintanance that it offered despite the car starting and running ok with its 051 distributor.
I had a similarly terrible time ''dropping'' the 123 ignition in due to the following issues and how I overcame them:
1.With the engine set at TDC/ roughly the static timing mark (only one scale of timing marks on my 250SL) the rotor arm on my 051 distributor pointed to number 1 spark plug.
With the 123 distributor dropped in and engaged (it'll only go in one way due to the offset key) its rotor arm pointed to roughly the nut on top of the power fluid steering resevoir (about 50 degrees out?)
I re-arranged the distributor cap so that the first spark plug wire that the rotor arm would contact would be number 1 and the subsequent wires inserted in the correct cylinder firing order as cast on the rocker cover (1-5-3-6-2-4 from memory, or is that my secret bank account password??
)
2. The 123 instructions describe how to obtain the static timing by rotating the distributor until the static timing light just turns off, but I similarly found that my car would not start at with the 123 set at this point. On examination I found the rotor arm to be way advanced from the number 1 spark plug lead at this static timing point so I simply rotated the 123 until it was very slightly advanced from number 1 spark plug lead and with an assistant to turn the engine over on its starter motor, I rotated the 123 very slightly clockwise and anti-clockwise until it started.
I then used a strobe light to check and adjust the ignition timing as per the haynes manual (there wasn't much in it).
The car has starting and running perfectly since with a steady even idle at 750 rpm, and accelerates without hesitation
. It was well worth the hassle.
I am still not sure why the 123 distributor cam is offset in this way (it cannot be adjusted, believe me I tried!!) but I'm sure that you should be able to get started again.
I hope that this can be helpful.
Charles