It's that 3RZ! Too heavy! Just kidding...
I can't tell you about high end shocks because I've never ran any. The rancho adjustables were OK and at full stiff they helped but after a few years they quit adjusting and were stuck on full soft. Now I run some big yellow monroes and they are about as good all around.
I had that same sway when loaded with camping gear and food. I ended up doing a few things and now it's gone completely.
The first thing was to ditch the common /\ rear shock mounting. This works great on pickups and dedicated crawlers but not on a loaded down expedition vehicle with a hard top. I ended up with my shocks nearly vertical and as close to the frame as possible. This helped enough to notice a difference.
Then I added leaves to my rear packs. I had some 3"lift chevy 63s with 4 or 5 leaves that worked great when my rig was a pickup. Not so great on the 4runner... I took off the lower arched leaves and added some stock leaves from some chevy 3/4 ton springs, the older 57" style. These were flatter stock leaves so they did not really add any lift to the springs. They might have even lowered about a half inch. I ended up with like 8 leaves total and an overload. I run 1 more leaf in the gas tank side to get an even, level ride. Oddly they still flex great and ride nice and smooth, even though they look like they belong on a 1 ton truck. I run rears up front. I peeled off all but the top three leaves and then added the lower 3 leaves from some stock front toy leaf packs. These look weird because most of the leaf material hangs to the back of the spring but it helps with handling some how. This helped noticeably.
Then I took off my 6"+ shackles and made some that were 3.5-4" like stock shackles, just beefier. I also put the cross braces in them with a bit of tube and a bolt sandwiching it tight to make them solid. At this time I also added stiffer than typical poly shackle bushings. This helped yet again.
All together I ended up lowering the truck about 2" and the bad sway your talking about is completely gone. It still has a bit more body roll in a hard turn than I would like when the top is on. When the top is off it rails like a bone stock pickup though! I would guess that would go away with a good sway bar setup or some really high end shocks. I'll probably try the sway bar sometime as I can't afford the uber-cool shocks.
I think Bigmike used a ford explorer front sway bar. I got one and it ended up being too wide to fit between things. It turns or he runs a wider FJ60 front housing so he has the room. Back to the drawing board on the cheap sway bar...
Good luck in your quest!
