2wd to 4wd Conversion?

[Goatman]

I might be looking at an 87' CC dually with a 4 speed standard trans that's a 2wd, 454 truck. I'm interested in it to do a diesel conversion.

How hard is it to convert one of these to 4wd? I would assume front springs, axle, driveshaft, transfer case with 4x4 selector. I'm thinking about going to a Cummins drivetrain, would it be easier to just swap in the entire drivetrain if I can find one with a standard trans? I thought I read somewhere that the transfer case of the Dodge were on the opposit side of the Chevy axle housing.