You should visit our club sitehttp://www.m-100.cc
and look at Karl Middlehuaves work with the 600's.He's the world expert but is considering retirement now.As you will see he has coupes ,hearses ,station wagons and a farm loaded with 600's.
Any body work on a 600 is wildly different to a regular benz,the average cost to restore all that wood veneer,installing it your self is around $10,000.and theres alot of leather in there to repair,$50,000 average cost.
Did you know they have total hydraulic control of the seats,boot lid and doors,it all runs off one circuit and on each seat there are dozens of little steel pipes.I think Karl requests $15,000 up front to rework the hydraulics on a 600.
The air suspension is the same as the 109 and W112, with the addition of a high pressure regulator.The parts such as the rear airbags all interchange with the 109.You will never see 600 parts on eBay..[:D]Although the occaisional restoration project pops up,and the average on those is around US $10,000.
The finny [8D],Putting a V8 into it is what the Germans call a "leggo" job,you just clip it all together.You can't do it with a PONTON though,totally different front crossmember and the engine bay is a bit narrow.the best bet is a twin cam 280.One from a 116 is the best bet,high compression and different cams to the 114 engine and miles more power than the US spec engine in the W126 280SE.
Up grade the brakes to 108/109 discs and you'r laughin'.With the W111 finny,the floor pan is the same as the 3.5 ,as is the suspension etc.Various little things like sway bar sizes etc are easily sorted.
The real hot set up is the M-100 6.3 into the W112 (300SE) coupe,Have a look at Karls two ,A convertible built for him by AMG and a black coupe he did himself.[8D][8D][8D]
My favorite will always be my 6.3 [}:)]