Today I finished cutting and crimping all the cables that I'll need for the 12 volt system. There are cables running from the two DC to DC converters and the accessory battery. The converters and the battery are all wired in parallel so that the voltage remains at 12, but the amps each provides gets added together.
The converters will put out a combined total of about 100 amps, and the battery will make up the shortfall if there is one. I expect when the power steering pump kicks in during hard turns, the draw from the pump and everything else running on 12 volts may be as much as 115 to 120 amps total. For that short time, the battery can pick up the slack. The rest of the time, the converters will be charging the battery.
I hooked the cables up and installed the battery into it's home. I haven't hooked the final "+" line up to the battery yet, I still need to insulate some of the lines. When I do, I intend to take the fuses out for each of the items I've installed, and then place them back one at a time to check each system. Hopefully that will make it easier to find any faults.