The W116 chassis Mercedes-Benz S-Class was presented to the public in September of 1972 with inline-6 and optional V8 powerplants. It was a huge car in long wheelbase variant and tipped the scales at a healthy 3900 lbs, but is known for a smooth ride and rugged build quality. If you are a Californian and have to deal with the state's draconian emissions test requirements, stick to the 1975 and earlier cars -- like this 1975 Mercedes-Benz 450 SEL offered for $3,000 in Marina del Rey, CA via craigslist.
The 450 SEL variant of the W116 is motivated by a 4.5 liter single overhead camshaft (per bank) 90 degree V8 that pushes 214 horsepower and 266 ft-lbs of torque in a 3-speed automatic gearbox. This 3900 lb beast isn't fast by modern measurements, but for 1975 standards it wasn't bad -- and still makes for a decent highway cruiser.
Today's example is the opposite of what you typically find in this price range -- usually $3k cars have nice interiors but are totally thrashed on the outside or need engine/trans work. This one is mechanically and externally fine, but the interior looks like it was home to a litter of raccoons. Perhaps you could pick up an el cheapo non running example to strip for interior parts and end up with one really nice W116.
See another sale on diving boards? email@example.com