How do I do this correctly? Truck is a 2011 Ford Super Duty 6.7L diesel.

 

Your truck is already set up to handle quite a bit of amperage without anything else done to it. You can use welders, winches, etc etc, its a beast of a work vehicle!!
Why do the big 3? Planning on 3000+ watts??

 

will have one (for sure) MRP-M1000 runnin at 2ohms, possibly 2. and a US Amps VLX-400 for the mids and tweets

 

Try contacting DC Power or Mechman
They might have something for you

 

Yeah, with double factory alts and batteries I doubt you need much. I'd do the big 3 just for good measure, but beyond that I think you'll be okay.

 

just follow the factory grounds from the bat to chassis and engine to body but put 0awg in its place same with the alternator to fuse block to battery

 

What he said, best way to do it, don't think you'll have power issues with that thing.

The cables on these new diesel trucks are already a good size already. I think all mine are about 4 to 2 gauge in size. I just bought a 2011 dodge 3500 diesel. It of course has dual batteries, but I didn't get it with dual alts and I doubt I'll bother doing the big 3 on it. So far I'm only running 1200 watts to two 8" subs without a single flicker of the lights. But I'll see what happens when I do the rest of the system in the spring, will be running 2400 watts with the amps capable of pulling 80 amps. I'll see how it does then.