Steve - notwithstanding worhtwhile advice you might get here, you might consider posting to the 300M Enthusiasts Club forums
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I know at least one avid poster there (SDMike) has a hitch on his M. Not sure if it's removable, but certainly he can add insight to your questions on brakes, tranny cooler (it already has one from the factory, but does it need more?), and towing capacity. I'm thinking, trailer or no trailer, that the LH cars aren't the most trouble-free as far as brakes (vibration - possibly warp-induced), so I would consider brakes on the trailer no matter what. Get Performance Friction Z-Rated? pads for the M - they are exceptional and cost no more than run-of-the-mill pads. Don't worry too much about the rear brakes - focus on the fronts - that's where the heat and problems are.
Might also consider replacing cooling fan assembly with police package replacement (which, believe it or not is actually cheaper than non-police - go figure!). Your fans are only good for about 100k miles anyway - so if the "opportunity" comes up for replacing them...
Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my adddress with the letter 'x')
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