First of all welcome to the forum.
Its the age old question really, but first you really need to decide what it is you want to do with the ute and how much weight you want to carry day to day and when you are out on the trails.
Once you know that then you can look at the different kits, if you are only going to carry a swag and an esky then what ever you do dont get heavy duty, in 4x4 terms heavy duty really means CONSTANT LOAD and if you dont want to carry stacks of tools every day you dont want heavy duty, the ride will be harsh and the back will sit too high not to mention it wont work well off road at all.
On the other hand if you do carry heaps of stuff 24/7 then dont go to the other end and get light duty or 150kg springs ect for obvious reasons.
Its also good to know what mods you want to do and what mods you are definitely going to do as things like bullbar, winches, canopies ect can and will need to be taken into account BEFORE spending your coin on your suspension
A good suspension supplier will talk to you about this in great detail and other swill just tell you what you need and probably will sell you the wrong stuff.
Not just because they are our Muster sponsors but because they are great to deal with Have a look at the links below in my signature, ZORDO, The Ultimate Suspension and Seldom Seen and their new shockwerks shocks.
Lots of members on here have used Zordo and swear by him, myself i have always had the guys at Ultimate kit out my utes and love their stuff.
Anyway have a look around and see what set ups people are running and ask questions to find out what you need.