The 8K springs are different, the axles, and the spacing between axles (hanger locations). I have one of the first 8K axle Redwoods, and they placed the axles too close together assuming they were the same as the 7K, causing springs to hit the shackles on the equaflex because the 2nd leaf is longer on the 8K than on the 7K. Per Engineering at Redwood, the fix for mine is to go to shorter shackles on the Equaflex, which they have sent me but I haven't installed yet to verify it will work.
Not sure what model 5er you have, but fully loaded and wet, I still only see 12,900 on the axles, which is well within a 7K axle system. Are you sure you need 8K?
Brad & Dory - Lone Tree, CO
CURRENT - 2013 Itasca Meridian 42E/2013 Wrangler 4dr Sahara
SOLD - 2014 Redwood 36RL/2014 F350 DRW