Do you guys really carry all that stuff? I'm about to drive from CO to SoCA to TX to MO to CO over the next few weeks. I will have a small tool box and my usual filters/belts, you can't possibly carry every part that might fail. Bring a cell phone and some money.

Yeah it's impossible to cover every situation.
Last year I drove my diesel converted fintail 3000 miles. Since the conversion was finished just a few weeks before the trip I didn't worry about the engine/tranny too much.
Of course something failed right after 150 miles - front brake caliper stuck. I brought with me all tools, filters, hoses, small jack and every kind of nut & bolt, but that didn't help. It just wasn't possible to repair a stuck caliper on the roadside..
(I had sheer luck when I passed a barn that had MB hubcaps all over it, stopped by and talked to the farmer who had scrapped a number of fintails and had a good caliper + not-so-worn pads for me for a MB-friend price)

Best advice would be to take most commonly needed tools with you, some filters and hoses.. AND get to know in advance what junk yards there are along the trip, where they are located and when they're open. Also get to know if there's any forum members or other MB enthusiasts along the road that'd be willing to help you if you get in trouble.

Good luck, those long trips are fun with older unpredictable cars

__________________
Tomas, Sweden
1966 Mercedes Benz 230S with OM617.912, automatic. Disk brakes from W108
1983 Mercedes Benz 300TD grey, OM617.912 and 5-speed manual
1983 Mercedes Benz 300TD blue 7-seater, OM617.912 and 5-speed manual