Hello RB -
Negative information only, I fear: my 280SL is number 004622, which I make as a roughly mid-August birthing in 1968, and still has a conventional ignition system with an 051, FWIW. It's a US version, picked up at the factory, driven around western Europe for a month or so, then brought over here and titled in the autumn of '68 as a new 1969 model, which was customary, I think. I've certainly not heard of anything like your setup showing up that early in production -- over 3,000 113s between yours and mine, still with its good ol' iron dizzy: very odd.
Easter's peace, All,
Denny