Has anyone actually done this? My '64 230SL takes an 046, 046, or 050 distributor per the Technical Manual, all of which are vacuum advance. I have the 123 installed and set to curve #6 which is the one called for for 046 and 050 distributors. But I'm getting very odd timing results. In particular, at idle I have the timing set to 10 BTDC. But when I goose the throttle, the timing retards 10 deg briefly, then goes back to 10 BTDC. If I rev the engine up it advances to about 30 BTDC which I think is correct. But I don't understand this momentary retard. Further confusing the issue, the retard behavior happens regardless of whether the vacuum line is attached.
I know lots of people have been very successful running these 123 distributors, but as I browse through the forum I'm not finding anyone who has installed one on an older vacuum advance car. I tried a 123 in a Volvo and discovered that some of their advance/retard programming is backwards, so to me they are all suspect until shown to be correct.