I'd also take a spare belt, fuel and air filters, and maybe a spare thermostat. Be sure your truck is in tip-top shape.
Did that trip in 2006. Long drive, but very interesting. Should have allocated more time to hang around once I got further south. If you're not going with a group supplying detailed advice (such as Vagabundos del Mar), some caveats (I'm sure there are more I haven't thought of at the moment):
Do not drive at night (animals on the dark roads). Don't go more than 55mph. Don't expect to cover much more than 250-300 miles per day, unless you're into endurance driving. Do not hurry through towns - the last thing you want is to get into even the most minor accident.
Be especially alert when heading up or down switchbacks - lanes are very narrow, there's usually little room to pull off on the side, and big trucks and RV's are coming at you. Go fairly slow, and be prepared to stop if you see a big rig suddenly appear heading for the same sharp turn you're heading for.
Make sure you have Mexican insurance (and fishing licenses if you're fishing), and take multiple copies of your drivers license, passport, and truck title and registration with you. Some of the rigamarole you'll have to go through won't make too much sense, but you have no option to skip it or speed it up.
Be patient and pleasant at the checkpoints - impatience will produce only resistance. If there are two or more of you, stay in the drivers seat and have another person get out and accompany (pleasantly) the people inspecting your rig. A woman with a big smile often can make things easier. A friendly dog in the truck can help too (bring rabies certificate and international health certificate). If you know a bit of Spanish, and try to respond in Spanish, that seems to be appreciated. Some of the military checkpoints are staffed with soldiers who do not speak English much at all.
Make sure the fuel pump is zeroed before your fuel is pumped, and have a good estimate of how many liters you should be getting before you begin. Gallons x 3. 785 = liters.
Know the exchange rates, and know how much you should expect to pay. Don't buy fuel (or anything else expensive) with US$ - have pesos - change a bunch before you cross the border. Don't buy fuel with large bills requiring lots of change - things have a tendency to get a bit confused.