Looks like a cool rig that has been used as intended: congrats.
I'm in the process of resurrecting a '72 that was off the road for an unknown number of years. I followed much of the advice already given, but have a couple more thoughts to add.
1) I would remove the carb from the truck and give it a good cleaning with carb/choke cleaner. If you carefully remove the air horn (i.e. the top of the carb) you can clean out the bowl and check the condition of the jets, needle and float, and accelerator pump. Reinstall the carb with a new gasket to prevent vacuum leaks.
2) Remove the fuel tank and have it hot tanked at a rad shop. It will come back squeaky clean but bare metal. If the tank doesn't seem *too* terrible, you can maybe get away with swishing some diesel around inside the tank. I like to throw in a length of chain in there too, to loosen up any deposits and flakes on the bottom of the tank. Rinse it out as best you can.
3) Replace the soft fuel lines and add an inline fuel filter if there isn't one. A clear plastic filter will give you a sense of what kind of crud is still in the tank, and will allow you to easily see if the fuel pump is working or not.
4) I like the Vice Grip Garage trick of using two stoke oil for the first start. Fill the carb bowl with it, and dump some right down the yap, as he says. Two stroke oil has more lubricity than gasoline.
Good luck!
Oh - and it looks like you're going to have to source some wipers!
