Install the newer S/C motor same bolt up as your current one. Reprogram the ECU computer using Kleemann, Now you will pay for this$$$ but if your keeping the car then do it. It's worth the effort to add a S/C to your car MORE POWER! and you don't have to buy a newer E55. Search the net you will find help out there. Call the aftermarket tuners Renntech, etc. There is lots of help if you have the money.
Here is some good info just to understand what the ECU is doing.
http://www.hs-elektronik.com/datenbl...s-e55-amg.html
If you want to tune by yourself with a dyno then here you go:
http://www.perfectpower.com/Products/smt6.asp
Have FUN!
