If you are running only a very light 12V load drawing only a few amps,then a tap off the dogbone would probably be OK. If you are running a moderate load, like a radio, a 24V-12V converter should work fine. If you are running a significant 12V load requiring a lot of 12V power,than a 24V equalizer would be in order if you can afford the bucks and run the truck enough to keep the batteries equalized. The alternative would be to add a separate 12V alternator and battery for your 12V load.