Stereo install not as smooth as I had hoped - have a couple questions

[Beatcoaster]

I am installing a Kenwood x493 into my 69 c10 and am having trouble getting it to turn on using the existing fuse box. Because of this and to keep the power demands of the unit off the old wiring, I will be hardwiring(with fusible link) the power lead directly to the battery. But even with that, functionality is off, so my questions are:

1. Does anyone know which wire color or spot in the fuse box is a switched 12volt that I can use? I tried what I figured would work but the deck won't turn on. Is there a space that is known to work?

2. Is the gray wire off my instrument cluster essentially an illumination wire? I want the deck to dim when I turn on the lights and was just wondering what others have used as the illumination wire on these old trucks.

Thanks!