Shmoo,
I guess that little note didn't help much did it!. A full wave bridge rectifier changes AC voltage to DC voltage. I don't know if that is what those things actually are, and I sure wouldn't know why they would be on the truck.
Because that idea is pretty bizarre, maybe they are something else. They would only be there if there was a special purpose intended for the truck or for that particular circuit.
They are not stock, and following the wires to their location might shed a bunch of light as to what they do...maybe the truck was a field operations station for the KGB and had a short wave radio installed with a direct link to the Kremlin.
Keep searching, you don't want that gob of stuff under your dash!
Secret-agent-Stu
