It is not. You need the HFM module and the EA/CC/ISC module and those need to be wired together as factory. So two rather large control modules and appropriate wiring to each other and the power of course. Then you need and ABS wheel speed signal going to them or you have a low RPM limit. I do not remember the exact number but it is around 3800 rpm or something like that.
Again there is info out there on doing this. I have a friend that did all factory stuff in a 190e with an 3.6 AMG.
So you are going to have to come up with an ABS sensor setup of some kind to feed the modules since a 450sl does not have ABS. I do not remember how picky they are or even if it cares to much what the value is or just that it sees something.
But then you have to find or buy a good HFM harness that is not rotten.
Then you have to figure out your gauges just the same as an aftermarket ECU.
Just more stuff is all and more requirements.