Mine were custom valving for the weight 25001-265. Call Ben @ Filthymotorsports. They will valve and have them built for whatever you like. Mine was valved to carry 800-1000 lbs over stock for high speed type driving.
Springs don't matter as much as the load you plan to carry. You may end up with custom springs depending on the load / height desired. I ended up with custom rear springs and spacer to achieve height and load capacity.
They work awesome! Only complaint... extremely difficult to adjust front coilover height when on the truck. I'd go with their stock front springs as well. I had the 600lb then went to 550lb and it was still a bit over sprung even with bumper, winch, skids, etc...
You'll need to clearance the upper a-arms to avoid contact with springs. Same problem with OME suspension.
Ride quality and high speed stability is exceptional. Makes the truck a blast on the back roads. Manual shift gears and run in AWD.