I did a 3" lift on my first disco and wrote up articles on that are still out there on the old Discoweb tech section. For reference:
If you want to keep your sway bars:
Sway Bar Disconnects:
In the suspenion install below, it also shows extended mounts for the front sway bar.
Front Drive Shaft:
RoverTym Suspension install. Springs, Flex Cones, Upper and lower mounts shock mounts, Trailing Links, Radius Arms:
For the 3" lift I did the stainless steel break lines and rear A-Arm extension. Also had some trimming of fenders. Will need more trimming if you go with a 3" lift without the radius arms, trailing links, and a-arm extension.
I thought there was an article on the a-arm extension, but I can't find it on there. Here is a link to it for reference:
https://rtefab.com/product/a-arm-extension/
I recall for that my mechanic also had to make a new brake line mount for the rear brakes was "taller". The one on there yanked on the brake lines at full suspension drop.
I also did adjustable Rancho shocks that were longer. I really liked them. I would stiffen them up manually for around town/highway and would soften them up for trail riding slowly. Keeping the sway bars and having adjustable shocks made my Rover feel very stable on the highway at speed. That plus wider offset rims and wide tires made it feel super planted on the road. No formal est data, of course, but I would put the on-highway manners as good or better than stock.
Miss that truck!
This was 20+ years ago, but feel fee to ping me with any questions.