Your stretching things now
I am really no expert, I only rewired my car with a kit.
Depends if you want the radio to operate all the time or just with the ignition.
For all the time you can go straight to the battery if you like. Other wise you will to find a "hot" wire under the dash or in the fuse panel that you can tap into.
For ignition only, use a test light to find the said wire or fuse panel point that is hot when the ignition is on and off when ignition is off.
Whatever you do make sure the wire to the radio is fused, one way or another.
Is it a custom wiring job or re-wired original?