[2011BaseV6]

Do a search there are some good posts about this. If you want the absolute stiffest rear springs, Lexus NX300h

2021 Lexus NX300 Rear Suspention Coil Shock Spring Pair 517-60195A OEM | eBay

This item removed from 2021 Lexus NX300 AWD. Rear Suspention Coil Shock Spring Pair OEM. Year: 2021. Make :Lexus. We do our best to resolve any issues within 24 hours. Interior Color: Black/Brown.

www.ebay.com

 

[DL175]

The Moog 81747 is what I recommend for you. It will provide similar performance as the Toyota third row spring at a much lower price. See this thread.

Buy from here: 2008 TOYOTA RAV4 2.4L L4 Coil Spring | RockAuto

For shocks either KYB or Toyota for the rear. I have the Sport model with the Sport shocks and it is firmer than the regular ones. Prices for factory shocks are competitive vs aftermarket and you will find lower prices online instead of going to the dealer directly.

 

[RevyRav]

I don’t think the Bilsteins you had prematurely died per se, you just need more spring stiffness. Probably literally any shock would be fine overall. The B6 is maybe better for more weight but you have lots of extra so anything will get worked, and the reality I suspect is you need more spring resistance just as you summized.

Northwoods offers an air spring kit for not much. Their metal springs are also much more progressive after 10% squish so you won’t work the shocks so hard. The MOOG recommendation is probably worth wild as well, anything over stock/KYB springs. The OEM sport ones are a little too linear IMO; they may be stiffer but they continually compress so confidence decreases the longer you’re into the corner and they’d still work your loaded shocks a lot more.