Darkhorse,
I get my 12v power two ways. I have a painless wiring circuit added to the truck. I recommend these because they don't place a load on your existing wiring. Also, I get constant 12v power from my fuse block (on the side of the dash). I got a piggy-back fuse from Pep Boys. They allow the factory connection to work, but supply fused power to your addition. Some guys don't like them and say they may vibrate out... I have had no problems for about 2 years. Just my . 02.
I forgot about Westach. I have a fuel pressure gauge from them now. They like power (12v). I had good luck with it but will replace it with a matching 30psi isspro mechanical gauge when the weather permits. jUst too darn cold right now.
Oh, yeah. You can get your illumination lights the same way. Unless you have already made a permanent connecition on the light switch itself.
-Jason