1:32 UH-1H

The only true difference between a D and a H model is the engine, The D had a T53-L-11 engine, the H had a T53-L-13 engine. In addition most H models left the factory with the pitot tube mounted on the roof, but some early H models still had the nose mounted one. Also most D models were upgraded to the H model during the course of their service. The only way to know for sure is to look at the door mounted data plate

In 1/32 there is the old Revell kit.  It is long out of production, but comes up on eBay frequently.  There were a bunch of boxings over the years as both a D model and an H model.  The kits are all the same though with a few extra pieces for a fictional US Army UH-1D gunship or different decals for other versions.

in 1/35, you have the Dragon UH-1D and UH-1H HEER SAR kits, or the older Panda boxings of the same as a UH-1D.  The Dragon ones are nice and contain a good PE fret that really adds to the details.  Dragon's are currently in production and should be easy to find.  The Panda kits are out of production and come up on eBay from time to time. 

The Dragon kits actually have all the parts in the box to build either a D or H model. You just have to know what to use for each version. For a straight H model, use the horizontal intakes on the engine cowling, right side tailboom panel w/o door, blade and towel rack antennas, pitot tube on the roof, and (depending on year) wire strike kit parts. You will also need to fix the main rotor blades. The kit has UH-1N blades, see below.

The Dragon/Panda kits have a few other issues as well.  Here is a run-down of things that need correcting/updating.

The interior is lacking and really could use the Cobra Company upgrade/detail sets. Most of the interior parts are oversized and chunky on details. On the outside, the rivets are too big and could use a light sanding to knock them down a bit as well. The rotor blade is wrong for a D or H model too. You can see how to fix them below, or Cobra Company has a rotor blade correction set.

The rotor blades in the D/H kit are the same as the N kit, but are incorrect for the D/H model. They are easy to fix though. In the below picture you see the kit blade in the middle (UH-1N or Bell 212 blade). The bottom blade shows the area in red that needs to be removed for a UH-1D/H (Bell 205) blade. The top is the corrected blade.

Both the 1/32 and the 1/35 versions will benefit greatly from aftermarket parts on the interior.  Cobra Company has some sets in both 1/32 and 1/35 for them.  Fireball Modelworks has some upgrade sets in 1/32 and some great decals in both scale.

Good luck in your search and post some pics once you get started on it.

I certainly will, ill be hitting the LHS this weekend to see what i can find. or order.