Where are the best wiring diagrams for our trucks?

[davepl]

I was trying to figure out the ammeter circuit, but the wiring chart I have is for a non-gauge truck and it just shows a different layout at the actual dash connection.

Where would I best look to figure this out (ie: what has the best wiring diagrams, is it the assembly manual)?

Thanks
Dave

PS: As I said, I have the big colored chart but that's for non-gauges as near as I can tell.