When we got the UniMoG, one of our first orders of business was to figure out what tools to carry with us in the truck on trips.  We quickly realized that carrying the truly big wrenches was pointless - if we had a major problem on the road it would require spare parts too big for us to carry, so we would have to find a place to work on the truck and get parts delivered to us.  When we replaced our transmission at to NWMF 2002, we were able to use Jim's large tools, and had most of the smaller tools required to do the job packed in the truck (a few were discovered to be missing, these have been added since!).  Essentially, we carry the tools & spares that would be required to do a tune-up.

The toolbox under the passenger seat of the 404 is big enough for almost all of the tools that we carry, we just had to figure out how to pack them all neatly so that they wouldn't rattle around.  Unfortunately, it turns out that a little too much moisture can manage to migrate into that box, and after several years we had to move the tool rolls into a cupboard in the camper --- after disposing of some badly rusted stuff.

These three tool rolls hold almost all of the tools we need.  In addition we also carry the tire wrench that came with the truck, a box of spare light bulbs (from Jim Ince), some zip-strips, a few bolts & wire connectors, a roll of wire, a large crescent wrench, a few rags & a roll of paper towel.

In the side box we carry the jack & jack block, tire chains, assorted bits needed for towing, & an oil funnel (spare fluids are carried in the camper).

In the jerry can holder we carry a water-tight ammo box with a spare distributor assembly (distributor column, cap, rotor, wires), coil, spark plug and spare rubber fuel & water lines (and more rags & paper towels).  (We realized early on that carrying a jerry can when we have about 400 liters of fuel on board was rather pointless.)

This setup has worked rather well for us.  Minor adjustments on the road are easily done with the tools we carry.