We use 2.5" Fox Coil Overs with Remote Reservoirs for our DMAX/HD Straight Axle Swaps.
We R&D'd several different coil rates and came up with the tuning below to create what we think is the best ride quality on a Duramax after a straight axle swap. Chevy HD's will need a different spring rate (call for assistance).
Our 8" Travel Fox Coil-overs run a Single rate Eibach Coil spring: 18" x 400lb spring rates.
Our 10" Travel Fox Coil-overs run Dual Rate Eibach Coil Springs: 6" x 500 lb and 16" x 400 lb.
Our 12" Travel Fox Coil-overs run Dual Rate Eibach Coil Springs: 10" x 400 lb and 16" x 500 lb.
These are sold as a pair and include the coil springs. They are charged with Nitrogen and ready to install!