I would use the fan off of a new C or E. They seem to be very efficient. Mercedes even did away with the auxillary fans because this ONE is sooooo good.
I would get a variable controller from Pep Boys and wire it in...Put the probe in the radiator fin. I have one on the 16v and it works great.
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS