This can be done. You will need the C32/SLK32/SRT6 engine with the ECU Engine harness and the other associated parts such as the heat exachanger. the heat exchanger from the SL55 is larger and better than the ones from the above cars. The mechanical swap is not that hard. You cannot just go order a ECU for this project. There is no CAN issues to check. The donor ECU must be unlocked and then reprogramed to the car using the Mercedes Star Diagnostic System in Developer Mode. You can buy cloned version of the STAR DAS system from China ad JC Recordings can sell you the key generator to unlock developer mode. Most MB mechanics have no knowledge of developer mode and it is in German only. It is a bit of a black art. Your best bet would be to do the mechanical work and then Have Rudy Compart do the programming. He can also do the entire swap. He is about the only one that can reprogram the ECU properly. He has been swaping 55K engines into Crossifres and other MB as well has a twin turbo V12 into MB that had a V8. Rudy is RCompart on Crossfireforum.org I used this same approach to swap a M113 V8 into my Crossfire.