Originally Posted by Dan Root
I found out the other day a Benz V-8 will fit easily.Check out the thread on a Simple Mod V-8 airbox,also you could probably buy a V-8 cheaper.
Yes the engine will fit. The problem is the wiring harness. My friend installed a 5.5 AMG into a C43 to make a C55. Everything is a breeze because the share the same wiring harness.
Crossfire/R170 SLK is still using the old wiring harness. You could tell by looking at how the ignition works:
R170 SLK/Crossfire -> you have to hold the key until the car start
Newer benz with V8 -> you don't have to hold it. The car will start by itself.
Having worked on a lot of Mercedes and dealing with their wiring harness, sensor, electronics, I know that this is no simple task.
As far as power, one of my friends has an SLK32 and After driving it(more like being inside a slingshot), I decided that it has enough power that I could handle. Any faster than that, not sure if that is good for me
Good luck with your search on V8 engine.