AC, vacuum locking doors and trunk, Becker radio that works!, rust
around the tire change jack points, jack, water on rear floor under
mats, seat horsehair condition, records on repairs preferably from an
MB certified shop, 0-60 MPH should be around 18 seconds, blow back from
oil filler hole ... bad rings, working tach and cruise control, look at
the oil filter area for oil on the vacuum line connectors ... was the
car stored inside? Take a drive and look for hard shifting. Some years
start in 2nd gear. Listen for noise down shifting (not manualy
downdshifting) from 25 mph. Tranny flair going into 4th gear. Does it
have MB antifreeze or green stuff? Are there any dark blotches in the
clear fuel filter? Does the engine shut off with the key? Shut off
engine, wait 1/2 hour and try the master lock. Does the owner have both
keys? Are the keys steel? Working power antenna? Assume everything
rubber is a time bomb. Look at the air cleaner mounts. If they let go,
air cleaner will hit the inner fender and make a hell of a noise.
But 1st you must ask your self if youre capable of wrenching and have
the $ to keep a 30 year old car running. Please don't fall in love with
an vintage MB hoping to use it as a daily driver without going over
everything. These cars are best owned by someone who tinkers with her
often ... maint. not repair.
Good luck.
I have a 1979 300SD and while I'm still getting the bugs out of the old
lady, she purrs on WVO. Nothing like the ride of a vintage 2 ton MB
getting 25 MPG at $.20 per gallon. Just wish my WVO would leave black
smoke. Getting tired of do gooders thinking my engine rings / valves
are shot.

$5K is a bit steep. She better be cherry with origional paint and all
maint records. You can't do a CarFax on the VIN (too old and the VIN
system won't work till '80s models)