G'day m8.
If you are going 6" your are going to need complete spring packs. You may also consider traction bars to stop axle wrap.
Have a search through this forum (top right of forum screen)
1999 - 2003 7.3L Power Stroke Diesel - Ford Truck Enthusiasts Forums
I did a quick "suspension lift"search .There are heaps of threads covering this.
Ford Truck Enthusiasts Forums - Search Results
It all depends on how much you want to spend. Have a read if you find what you like the best bet is to ring the supplier. You will find the guys in the States very helpful.
You can also speak to Clay at Riffraff Diesel. He is a sponsor hear and very well respected
Riffraff Diesel Performance Parts: Powerstroke Parts | Ford Diesel Parts | Ford - 99-03 Super Duty 7.3L
He has some suspension lifts that Im interested in as well. Im keen on the lift blocks with the traction bar as one unit. Then all I have to do is get a spring pack for the front
Riffraff Diesel: One Up Offroad Traction Block & Traction Bar
Do some searching then heaps of reading and ask plenty of questions.
If you have heaps of money like Nkelly you could go full airbag. Have a read of this
https://www.ford-trucks.com/forums/1...e-r4-tech.html