That would be a neat mod. All that torque and HP would be wasted on the stock 49 3100's drivetrain so you're looking at an engine to rear swap.

I don't know what the weight of the Cummins is but I'll swag it's atleast 100lbs if not more heavier so you're looking at beefing up the straight axle front end.

Wonder if a 3100's cab & bed would fit on a Ram's frame?

Anythings doable, it just depends on your skill level and available funds....
Good luck
Dave