As a 30 year automotive technician who is eccentric about everything having a place. It's absolutely necessary to have all 3 sizes of ratchets. You will need 4mm to 13mm in 1/4 drive that's both deep and regular size sockets. In 3/8 drive 10mm thru 19mm both standard size and deep sockets and for half inch drive deep only will work from about 10mm to 24mm and if you need bigger get a hub socket set with 28 to 36mm. There usually 6 sockets in that set. The open and closed end combination wrench's you will absolutely need. Size 10mm thru 19mm and I would recommend as many sizes you can get up to 30mm. A very large Crescent wrench can be used for anything bigger. You will need a big pipe wrench also. They have either online or at harbor freight socket organizers where you can put them all in either smaller sets or a few bigger ones. I recommend into sets grouped like above. Also there are wrench set organizers for your drawers of the tool box.
A long magnet is good to put in there for misc things. A breaker bar of 1/2" and a good 18" in length is good. If you need more always a cheater pipe. A cheap multi meter that has ohms and DC volts is all you will ever use. A test light also is good to have. Especially for finding a draw. Everything is going to be metric on your van. PS the diagnostic link on those vehicles can be done by jumping terminals A and B with anything that conducts electricity, wire, paper clip. It will display your trouble codes on the dash in the form of a flashing light. The check engine light.
You can store all the above mentioned tools in a small waist high tool box and still have tons of room. If you want to get fancy you can get styrofoam and cut out the shapes of your screwdrivers and wrench's (pliers types) this works well with something around 1" thick. Cut them close though or you will run out of room quick. Leave the extra space there so you can add tools to the drawer as needed, just cut a new hole for it. Your tool cases are usealy too big so get rid of them as this will eat up room in your box. Lastly make sure your toolbox rolls. It's so much easier to just roll it next to you then you can use the top as a workbench while doing repairs. So you don't have to go constantly go back and forth.
Take pictures before you start of what your working on. It's invaluable later when you forget something. Also a small magnetic tray helps with small parts while your working so they don't get lost and if your doing some large project a small space organizer with a bunch of compartments works well. You can add notes or number them and even makes numbers on the engine as well with a paint marker.
