sell a Ford and get a chevy??? Now that's just dumb. You'd be sacrificing tow capability. That, and Chevy doesn't offer an 8-9 passenger vehicle with a diesel... PLUS Chevy has their ridiculous IFS system up front, great for comfort but nothing else on a HD truck...
My friend has bags on his SRW F-350 with a Pro-comp 6" lift on 37" tires. He's towing a 17,000 lb trailer with an ls2 funnco inside.
He said he got his bags from 4wheelparts and spent about $400. He bought an onboard compressor later on to fill on the fly. Whole system ended up around $700 with dash gauges, bags, compressor, wiring, dash mount fill controls.