Indeed the BDS lower longarm kit is just that lower arm's and frame brackets, it is meant to be used with a 5"+ lift kit that already has upper control arm relocation brackets and arm's.
Some move the upper arm to the lower arms old mounting bracket on the frame, upper arm will be in the 18"-19" C to C. I would have a reputable machine/fab/welding shop make up a set, you buy all the ends, tubeing adapters and misalignment parts. They weld it together for you.
There are a few other long arm kits out there you might keep looking around if you want a full long arm kit.
This is the Fab-Tech long arm kit. I like the upper control arm bracket much more over the BDS or Skyjacker ones as these are made out of thick steel and are inserted over being a metal wrap over the old upper arm brackets like BDS and Skyjacker use.
Top cut off the factory upper control arm mount, ready for the Fab-Tech mount.
Upper control arm brackets being installed.
Fab-Tech upper control arm mount's.