Just did the exact same thing last week with a '73 350 SL
that had been sitting in Marin county.
Here's what I did;
drain the gas tank, flush it with a gallon or so of new gas
drain the engine oil and radiator fluid, replace with new
new oil filter
remove all spark plugs, and put a small amount of engine oil
in each cylender
remove high tension wire from coil, and crank the engine
until you get oil pressure, then crank it a bit more
this is a good time to check compression....this will tell
you if there are stuck valves, or other serious problems
replace the spark plugs, coil wire and fire it up!
of course, check for cracked fuel hoses, belts and brake hoses
before driving it