Check the overall width of your duals (outer wheel to outer wheel) versus the overall width of the duals on the truck with the dually bed.
If I remember correctly,
With duals swapped onto a single wheel 14-bolt rear end (C/K-20 rear axle), the total width (outer wheel to outer wheel) will be narrower than duals on a dual wheel 14-bolt (C/K-30 dually).
I'm thinking that the dually bed will physically swap fine, but the outer dual on your truck will be set back within the dually fender...