GU Y61 Suspension Questions - Please Help

[HankyBoii]

Hi all,

I'm totally new to suspension and just trying to wrap my head around all the different components and their functions.

I have a few questions to ask you all... any help is greatly appreciated.

Context: I bought a 2004 GU Y61 Patrol about 2 years ago. It has always been a harsh ride, you feel every bump in the road and on longer drives, you get a sore lower back from the jarring bumps. The previous owner claimed the car was setup for towing and he thinks he installed 2" lift springs which he claims are 300-400kg springs. I'd really like to improve the drivability of the car, as I am about to start on my lap around Australia. 99% of time it will be used on-road, however we do like to go off-road occasionally for a bit of fun (nothing serious).

The Springs: I don't know what are on the car at the moment, there are no part numbers or markings on them. I did some research and found that you can measure your ride height to figure out what springs are installed... here is the data:

Stock GU Values (Center of wheel to guard):
Front 550mm
Rear 560mm

Measured on my car (Center of wheel to guard):
Front 580mm
Rear 540mm

Not too sure what to make of this??

Shocks: My car has upgraded shocks, they are:

Front - Toughdog FC41047 - LINK
Rear - Toughdog FC41206 - LINK

Looks like they are suitable for up to 2" lift

Additional Info: I just recently found a pair of front and rear 2" King Springs on marketplace for cheap. I got a set of KDFR-42HD front springs and KDPR-58LP rear springs which I'd like to put on my car to replace the current setup.

It also seems like I have upgraded toughdog steering dampner too... not sure if panhard has been replaced, but I do get a noticeable wobble at around 80kmph.

Weight of car: Fully loaded with 2 people and all our stuff we weigh in at 3.1T

Accessories on the car are as follows:
- Stock alloy bar and stock rear bar
- Second battery
- 95kg Roof top tent
- Kings drawers with tools and other camping essentials
- Removed rear seats and put in a wooden tub for storage
- Rear of car loaded with plastic tubs with clothes, shoes, fishing gear and cooking gear

Questions:

1. Will replacing the current springs with the king springs make much of a difference?
2. Do you recommend I upgrade the shocks at the same time, or are these ok for my needs?
3. I feel like due to either additional weight or spring sag, the rear of the car is hitting the shocks bump stops, do you think this may be the case?
4. Could something else be causing this very hard ride?
5. Will I need anything in addition, for example caster correction, extended brake lines, etc.. if I replace the current springs with the new ones?
6. Anything else you would recommend me to check for before doing my lap?

Thank you in advance!