Hi Ed...
The old MBs are great when they run fine but can drive you nuts getting them to that point. I don't know if it will help you here, but the British use something called a 'unisyn' to balance carbs...it has a plastic ball that lifts to measure the air flow through each carb...they cost only $20 or so and are basically a thin venturi with a draft gauge attached. One thing to be aware of with the early MBs is that the distributor can 'walk' up if not tightened down. Dumb design having a hex nut pointing toward the fan you cant see but have to feel for...I've had this happen to me many times setting the timing on my 280SL...just when I think everything is set, loss of power and sputtering happens when my points move and/or that distributor starts to lift up (and with a flaky condenser). I run mine also using points to trigger and electronic ignition so I have a backup on the road if I want to run full current through the points if the electronic fails...whatever, suggest you get an electronic ignition...it will make your life much easier while chasing everything else. Only like $130...good luck...keep us informed...