I'm not 100% certain, but reasonably confident that you won't find a fuse block on your Jeep. What fuses you have are most likely inline.
Going with that, you'll most likely want to find a "switched" hot lead and splice on to it for your power. You can ground to the body, just be sure you get a good contact.
Here's a link to a 1974 CJ5 wiring diagram:http://www.offroaders.com/tech/Jeep-...74-1975-CJ.htm
That diagram DOES show a fuse block. You maybe able to tap your power from there, maybe even a provision for a radio!
My GUESS is that a CJ and a DJ shared wiring looms. Good luck!