hi truckernix,
the coil is about 4 ohms cold, so with good wires from 6.3V it would be about 1.5 - 1.6 amps in theory.
my power supply shows 1.34 amps but i'm likely suffering from a lot of extra lead resistance in those skinny wires and the alligator clips.

if your generator is running well and the truck is at about 7.2V then the coil would be linear in that range and should go up to about 1.8 amps.

The specification for the radio is 6.5 amps max @ 6.0V input, which includes the speaker. That makes sense from what i recall with the last one i fixed up, radio - speaker was in the 4.x amps.
-s