I'd get tubing suitable for an axle, two stub axle/hub assemblies, weld flanges to the axle tub drilled to match the stub axle and bolt the sub axles to them then fit the hubs.

 

Eventually I'm installing a starting battery in the boot so, in support of that, I ran a #2 welding cable from the main feed at the starter stud along the chassis side rail to the rear can came up through the bottom with one of these:


I then ran a #10 cable to a Blue Sea fuse block:


From one of the terminals on that I ran a #12 to the trailer connector. In my case I'm just charging the trailer brake battery so #12 is plenty.
What load do you expect to have? That (and the distance of the run) is how you really choose a wire gauge.

 

That sounds way more complex than it needs to be.

What did you hook your battery cable up to? Alternator or your truck battery?

 

Yeah, more complicated than just for a trailer, but I'm planning additional electrical loads so was allowing for future expansion without having to redo things.

It's connected to the main feed at the starter.

 

Did you just find it easier to attach at the lower point? That stupid heat shield made it a bear to swap out the starter that is why I am thinking of connecting it at the alternator. Means about 4 extra feet of cable.

 

Ah, well, there's no heat shield on mine.

You haven't said what the expected load is. You might be ok just tapping in to the trailer aux power circuit in the boot.

 

I did not realize there was a aux wire until I checked the wiring layout again. I am just looking for a trickle charge while I drive.

 

Then that should do you fine. It's protected by a 20 amp fuse.