I've scanned the thread and wanted to add that the helper bags will help a lot. Another option is the Firestone R4Tech kit. It's pricey, $2000, but it's air over leaf and takes all the OEM spring out.
Option 3 hasn't been mentioned at all - Sulastic shackles. I've got a set ordered for my 08 GMC 3500HD dually, so I'll write a report in this forum once done. Lots of video's here to see how well they actually help.
https://www.sulastic.com/Default.aspx
http://www.alligatorperformance.com/sulastic-rubber-shackle-0108-duramax-p-3054.html