Originally Posted by blackout
Has anyone come across a lightweight, but safe, larger 4x4 rim for these trucks? ..
Aluminum is about as light as you're going to find at a reasonable price.
Ford SVT made one for the 2004 model year SuperDuty that will fit your '99-'04. It is 18" x 8", so it will take a pretty big tire - up to about 285/65R18, which has a 11.5" section width, and is about the same diameter as your current 285/75R16. Michelin LTX/A2 and BFGoodrich AllTerrain make that size tires.
These wheels were made for 2004 SuperDuty trucks, so they are the correct hub-centric wheels for your truck. Ignore the "4x2" description on the first one. There is no difference between 4x4 and 4x2 SuperDuty wheels. These two wheels are identical except one has the Harley-Davidson logo and the cheaper one doesn't.
SVT F250 4x2 Truck Polished
SVT F250 2004 Harley Polished
Your current 285s require 7.5" wide wheels, so they are too wide for your 7" wide stock wheels. But if you feel comfortable running with tires that are too wide for the wheels, then you might could do the same thing with the 18" wheels. In that case, 305/65R18 require 8.5" rims, and are 12.2" section width with 1/2" more diameter than the 285s. BFGoodrich AllTerrain makes that size. But be ready for sticker shock of about $300 each.
My Sierra Blanca in the sig pic was a great pickup for 11.5 years. I sold it a coupla years ago. I drove a hand-me-down 2003 F-150 SuperCrew 4.6L 2V for a while, but it was unacceptable for towing more than a rowboat. Replacement is a 2012 F-150 EcoBoost SuperCrew Lariat that tows my 5,000-pound TT like a dream.