Pretty sure that they're in the same place, W202 with the standard analogue heating/AC controls (dual zone) and a facelift CLK with the same setup were both in the passenger footwell.
Re - the charcoal/pollen filter comment - isn't there two types of possible fitments for ths same filter. Ie, a charcoal type and a regular filter - both fit in the same place though (?)
Might be confused, but I seem to remember something like that
Will