My answer to you depends on if you can weld *well* or not. If you're not sure, welding something you need to stay together might not be a good project

But assuming you can, here is more or less what you want to make. You might be able to google some additional results. I wouldn't worry so much about googling for F350's specfically, as for pickups they are more or less the same design - just that the mounting brackets would be different because the frames are slightly different, and have holes in different places, for Dodge, Ford, Chevy, so looking at other kits for different brands might give you more ideas.

http://www.stengelbros.com/catalog/8...63_5212876.htm

http://www.airbagit-store.com/produc...t.asp&ID=92981

http://www.stylinconcepts.com/parts..../categoryid/30


This 6mb PDF gives you details in how to install it, which you might get enough detail to design your own:
http://www.linkmfg.com/PDFs/Updated%...174_060323.pdf

Some of the designs above are 2-arm designs, which work but I'd still be worried about the pinion angle changing while the suspension travels under load. Like you said, transit bus type vehicles have this feature nowdays - they're called kneeling busses. They drop the front at the curb so passengers can step in and out easier as the floor of the bus' stairwell is lowered to curb height.

BTW, the longer the 2 arms, the less the pinion angle is changed with suspenion travel - one of the reasons why a lot of off-road guys do use 2-arm rear suspensions and have the links mounted under the cab...