I don't recommend tapping your radio wire. If anything you could do what I did which will make things a little bit easier and it adds a fuse inline so that you don't run the risk of frying any of your new toys. There is a thing called an
ADD-A-Circuit and it plugs right into your fuse box. They sell these at any auto parts place. Then you find a fuse that is ignition power source. I used the cigar fuse since it comes on with the key. This only comes to a single wire but not to worry since it is a decently thick gauge wire. I would also get a power distribution block so that you can run that single wire power source to the block and voila! Now you have multiple places to wires gauges or what ever you have that needs a 12v ign power source. I used this as a
distribution only bigger, which I got at radio shack and I just bridged the connections on one side and it left me with 6 connectors for gauges, wideband etc. Hope this helps and if you need pic lmk.