I noticed the Spring Collar missing!
Jet and plug swapped...But an expert tells me that's not a problem
I swapped them back...every M 74 B I have has the jet on the left
A spare Spring Collar installed...
After a full inspection, swapping the jet and plug back to the "normal" positions (even though Linkert expert "Cotton" tells me that doesn't make a difference) and installing a spare low speed needle spring collar, I re-installed the carb, reset needle adjustments (5 turns out on the low speed and 1 3/4 on the high speed) and fired it up...it worked as normal (a bit too rich as it should) and I dialed it in.
The Pan now starts on one kick, idles nicely and revs up like a dream. Too much ice out there to road test...but all systems are now a GO!
So it looks like the spring collar missing made all the difference! Too much air getting past the Low Speed Needle!!!???