Best suspension for towing and twisty highway driving

[poseidon]

I have an 04 GX. For the trails and backroads I usually use one of my more capable cruisers. My GX is used as a daily driver and for towing our small Airstream and cargo trailers for work. When I tow the Airstream I do use a weight distribution hitch. For work I also have to drive over a snowy mountain pass several times a month during the winter. I don't get paid by the hour so I usually take the winding highway corners fairly fast if they aren't a sheet of packed snow/ice.
Lately I have been noticing that the suspension seems to be acting funky. It will sometimes be very high in the back and then on other occasions squatted down. We went camping for memorial day and had it loaded down with RTT and gear and it was squatting like a dog that needed to dump. The ride in the back is occasional ridiculously bouncy too. I lubricated the elbow and looked at the two sensors and have listened to the pump and it is shutting off, not running constantly. So there are no obvious outward signs of what the issue is to my untrained eye/ear. The GX has around 175k miles and likely the original suspension components. I want to keep this rig close to stock height for comfort and highway cornering on the winding passes.
I am wondering what direction to take the suspension refresh. I can get some new shocks, replace the airbags, and get 2 new sensors off ebay and hopefully that will get it going back down the road in stock form.
Alternately I could eliminate the hassle of the adjustable airbags and go with a spring setup. A 4runner guy of questionable intellect told that an Icon setup was the best for towing but I would certainly want to verify this.

What is the wisdom of the internet? Should I update the existing system or not? For ether route what are the recommended specific products that would be best for making it ride and tow well?

I have also tinkered with the idea of selling this as is and getting a tundra so PM me if you really want an unmolested highway queen that needs a suspension refresh.

 

[GXer04]

I've seen some guys with Dobinson's springs with internal airbags. I tow our camper, so that's what I'll probably do. It should give you a good ride unloaded and give you the option to air up the bags for towing and heavy loads. If someone has this setup, chime it because I'm thinking this could work for me.

 

[Sleepy]

I tow with Firestone bags and Dobinsons springs. Works great.

 

[HomersCanyonero]

If you care about lowering the rear to hitch the trailer, then try fixing them. Usually, the airbags leak air and just need to be replaced. There are cheap aftermarket replacements. Unfortunately, you sound like you have other issues.

If I were in your situation, I would do the rear coil conversion. I would use these progressive Dobinson springs which might get you like 1.5" of lift in the rear:
C59-675V - Variable rate comfort option, stock rear weight, 3" lift. 470/470mm, 16mm wire, 157-230LB variable

Get the spring conversion kit from either MetalTech or SSO. It's about $230 for this kit. Add the firestone airbags when towing.

If you want to refresh the shocks and front coils, then look to see if you can find the close out sale on the Toyota Trails Ultimate Edition suspension for $573

Part # PTR13-35140

Kit includes:

-2 Bilstein front shocks 2.5" diameter (non-adjustable 6112's)

-2 Bilstein remote reservoir rear shocks 2" diameter (5160's)

-2 red front coil springs (restores factory height on GX470 +/- 1/2")

-all hardware to put everything together and mount everything up