Dodge Ram Van Components in A Body?
Being a 3500 series, it has an 8 lug Dana 60. The money spent to make this fit would surely exceed the cost of an 8 1/4" axle or a Ford 8.8.
Do a search here on the Ford Explorer 8.8 axle for use in A body cars. These can be bought for under $200 and they all came with the 4.5 bolt pattern, 3.73 or 4.10 gears, a limited slip differential and disc brakes. Some work is required to get them to fit but many members here have done the work themselves.
The Van transmission is likely a 4 speed automatic overdrive and depending on the year model, it may or may not need a stand alone computer to make the 4th gear overdrive to work. These transmissions are also physically larger than any classic Mopar transmission tunnel so be ready to do some cutting and welding to the floor.