Getting parts is not a problem at all. You need to find an experienced Off Road shop to do your work, not a Ford Dealer and not PEP Boys - someone who knows what a Dana 44 or 60 is and how 4x4 suspensions work.
The real issue with an Advanced 4x4 conversation is ride quality. If you can accept the ride quality of a short leaf sprung suspension and the van suits your needs and price point, get it checked out by a good mechanic and go for it.
Four time Baja 1000 winner, four time Baja 500 winner. Solo'ed the Baja 1000 to LaPaz/Cabo twice.
4-Wheeling since 1972, Desert Racing since 1989.