what is a six stud steering arm with the trail gear solid axle swap?
the stock steering arms bolt on to the knuckles with 4 bolts (actually, they're studs with nuts on them). With huge tires and power steering, it's possible to get in a situation where it's easier for the steering to break those 4 studs off than it is to turn your wheel. It won't make much sense if you haven't had a good hard look at a toyota axle before.
the 6 studs make it stronger so now it has to sheer 6 studs instead of 4. You can also upgrade the bolts to a stronger material (ARP studs) to reduce breakage as well. If you're new to wheeling, it'll be a good year or two before you get in situations where you'll break your steering studs, unless you're running tires bigger than 35's. A lot of guys run stock steering studs on huge tires, they just make sure to torque those nuts down before (and sometimes during) every ride.
Basically, I wouldn't worry about the 6-stud steering arms unless you've got a big budget for this build. Do the bare minimum first: sas, steering, sliders, 4.7 t-case gears or dual cases, and go from there. That alone will set you back more than a grand. You'll then want to add lockers, which add to the cost, then gear the axles, then get big tires. So plan on $3-4k new for those mods, and that's before you get to the 6-stud steering.
I run the 6-stud steering with the arp studs because I wanted my setup to be bulletproof, and I could afford it at the time. It's overkill for my needs, but now I don't have to worry about breaking that. I also run dirty 30 axles, hardened hub gears, and hardened hub studs for the same reason. Totally overkill, but my motto is, if you're going to build something, build it right. My front end could easily handle 40" tires with the way I drive.
Do you have any pics of rigs that are similar to what you want to build? Is it going to be your daily driver? What tire size are you shooting for? We can give good advice on your build if we know what you want to do with it: we've been there and made the wrong mistakes.