Pawel
I didn't see any builds of the new baby yet, but if it's really this good and you want to get funky, you might transplant the Italeri engines on the -D fuselage - that could get you a nice model!
The Kitty Hawk UH-1D is really nice, just not my scale. They are supposed to do one in 1/35, eventually. I can't wait to see how that one looks.
Here are a couple builds of it.
Aussie Air Force UH-1H http://www.arcforums.com/forums/air/index.php?/topic/300692-148-kittyhawk-uh-1h-9-sqn-raaf/
US Army UH-1D http://www.arcforums.com/forums/air/index.php?/topic/299774-kitty-hawk-148th-scale-uh-1d-finished/
It also wouldn't work to just slap the Italeri N parts on the KH D model to make a nice N model. Firstly, the Italeri parts are nowhere near as nice as the KH ones. You would also need to add a lot more than just the engine area. The N has a different nose, new main and tail rotor blades, a different instrument panel, etc., etc., etc... It is not just a dual engined UH-1D.