Think it's shocks

Hey loving 4Runner fam
I got a 2001 black beauty. Bought him as a little pup, just born, from a dealer in Minneapolis. Tommy now has 340,500 on him (all driven by me or the wife or the eldest daughter - never again lol).

He's now living in Cali so his hard midwestern days are behind him. And apart from some welding underneath and regular repairs for one thing or another he still drives like the king he is. A little grey around the edges but that just adds to the AUTHORITY right?

Anyhow, he's started to show this weird shimmy at speed on bumpy Interstates (still drive him 20,000 a year). Like a rocking, swaying thing. Not steering, not sway bars. I assume it's shocks. Thoughts?
Jez

 

Have you balanced the tires lately?

 

as the rear sags the shocks get super bouncy, perhaps you need springs and shocks.