I think your brakes will be fine. I'd change all the brake lines over though to Stainless steel- just a bit of insurance, and also switch to the DOT 5 (synth, but dot 3 compatible) fluids, with a full bleed. Much higher boiling point.
Some really good front pads (might even want something like a semi carbon/kevlar based one).
Oh yeah, and add airbags for the back. you'll definately need it.
Other than that, go for it. Aerodynamics wont be that bad, think about it like pulling a 5th wheel. If you have the money, you could also consider swapping to 19.5" wheels. They have a significant margin of weight carrying capability (rickson wheels, for one manufacturer).