Here's a quick update.
All four boys are back at my shop now. As soon as I have them all in one room, I'll snap a picture. Maybe someday I'll get a lift, then they will have bunk beds:)
Anyway, I've remain focused on the '70 280SL mostly because it's the only one with a 4-speed. So far I've flushed and cleaned the gas tank, replace filters, replaced the plugs and wires, installed a Crane ignition system, replaced the clutch hydraulics, adjusted the throttle linkage, adjusted the air bypass mixture, un-seized the wipers, by-passed the dash light dimmer, removed the heater lever assembly to replace the levers (waiting on one more lever to finish it), put the cooling system back together, ordered new tires, fixed misc lights, got the car running, and drove it around the barn yard. It seems to run well, but I won't really know until I take it for a real test drive.
Now the car is on jacks with one side of the front end apart for a re-build, but I got replacement king pins that appear corroded on the bearing surface, so I need to return them for another set.
The list of unknowns is getting shorter and sorter - at least for this car. Still three more to go.