Don't know if this helps...
Hi. Looks like no one has given you a reply, so I'll try...
I believe the SL500 has the same basic M119 engine that my 1996 S500 has... except it has an earlier ignition system.
Anyway, when you say "left side" do you mean the passenger's side?
On my S500, the air (smog) pump is mounted directly beneath the passenger side (right) cylinder head and right beside the fan.
The bracket that holds it to the engine also mounts the alternator and an idler.
The alternator hangs beneath the air pump and slightly towards the crankshaft pulley.
The idler pulley is about 3 inches in diameter. The idler pulley is higher then the air pump and directly above the alternator pulley.
Hope this helps.
Hard to understand how this hooks together if you don't have the bracket... so, top to bottom its idler, air pump, and alternator.
Maybe there's an SL500 guy here who can send you a pix.
Hope this helps, KenP