These engines have been put into various other cars before. Mechatronic do them, Chrysler Crossfires get them, and I even saw a 1955 Buick got the entire driveline from an ML55!
I have an M113 E55 AMG engine and trans that I bought to put into a W112 coupe - but it is basically the same as a 108. it is still not clear to me that it is going into a 108, but really if the electronics are the worry then it is no different. I did a bit of homework, but not exhaustive yet. I am a little way off doing it. But recently I picked up a W126 500SEC that I am umming and ahing as to if I put it into that...
- pretty much any decent engine management system can get the engine working. Fuel + spark + ignition, and it does have a variable intake length intake manifold that most can also make work. In Australia we have Autronic , Haltech and the like
- the trans controller has been hacked by a few people now - so you don't need to throw it in the bin or give your first born child to Mechatronic. See here - New 722.6 Gearbox in you old Car | Mercedes-Benz turbo
- I saved this link as it has a contact in the USA that has swapped these motors into Chrysler Crossfires. Want to Wake Up a Sleepy Crossfire? Drop in a Supercharged AMG V8! - Hot Rod Network
- if you want to keep all the immobiliser system working, try this Rudy fellow - https://www.linkedin.com/in/rudy-compart-b20b3a7
- for a rear end, the easiest is to get a complete rear end from a W109 6.3. It has the same diff ratio as the W210 E55. You also get a rear sway bar and air suspension if you want. They are pricey though.
- another option that a mate is doing here is swapping in a complete rear end from a W126. You get a choice of diff ratio's, and true independent suspension. Just more fabrication. Look under a W126 rear at a wrecker and you will see how it all mounts off 3 main points. I can provide a bit more info if that is of interest - I am a bit pushed for time right now, but this is exciting and I couldn't help myself!
- Your client needs to figure out if he wants to replicate all the ESC etc stuff. If so, then you will need to figure out mounts for speed sensors on each wheel. There was a thread I had saved from Benzworld about Ron Cavallo from memory who put a V12 into a R107, and he did all the sensors. Long project.
I have some notes scribbled down somewhere from reading a whole lot of forum stuff but don't have time to dig it up right now. I will keep an eye out on this thread and hopefully we can steer each other along.