The Iowa class battleships were arguably the best to serve during WWII, and they had a long career after the war lasting into the 1990s. It is interesting however that the most well known (and hence most modelled) ship of the class is not the name ship, USS Iowa, but USS Missouri. Model manufacturers have always chosen to do “Mighty Mo” in WWII fit, and when they do any of the others it’s usually a re-boxed Missouri. In 1:350 scale there are conversion sets available for those who wish to build Iowa, but in 1:700 you have to scratchbuild. This is the step by step story of my project, to convert a Missouri to Iowa in 1:700. There are significant differences between the two ships and I will try to cover them as best I can; hopefully there will be more 1:700 Iowas around when you’re done reading this.
OK then, first things first, here are the various items I used for this project: 

Tamiya 1:700 USS Missouri
GMM 1:700 US Battleships PE
GMM 1:700 Doors, Hatches & Life rings
GMM 1:700 20mm Oerlikons and shields 
WEM Colourcoats: 5-L Light Grey, 5-N Navy Blue & 20-B Deck Blue

Before gluing anything, I removed the middle deck section from its sprue and, with a very sharp knife and significant amounts of force removed those awful “Aztec steps” to be replaced with proper PE ladders at a later stage. Also I removed the moulded-on lower bridge windows, to be replaced by the GMM PE windows later on. Then just build the kit as per the instructions to the stage shown on the right. click images
to enlarge
The most notable difference between the two ships is the construction of the bridge: Iowa had a round open bridge. Images 2-6 below show how the kit parts were first cut and shaped correctly and completed using styrene strips for and balsa wood to create the armoured conning tower. After they are put together the upper bridge level (unique to Iowa) can be built from styrene sheet and the shields added, made from the stainless steel from the photo-etch fret. The ribbed appearance of this shield is achieved by placing vertical ladder stock across it. Note that the support for the forward director has been sanded to make it shorter and glued on top of the deck level.
Now back to the ladders. Where the steps have been removed I cut a small rectangle of the stainless steel from the PE fret (very useful material) and glued it to the superstructure so the ladder can be attached to it.
 I continued building the superstructure and adding PE until the ship was almost complete. I used some thicker stretched sprue to make the supports for the AA gun positions. The PE from GMM is pretty self-explanatory. At this stage however I thought it was a good idea to leave off the doors and hatches.
There are a few other differences between the two ships. The forward tower has an extra platform protruding forward at the level of the top of the funnel, and this was made from styrene sheet. The platform below this is supported by a simple rod structure made from stretched sprue and it also has a “ribbed” appearance. For this I used the same technique as on the additional bridge level, ladder stock placed horizontally on the outside of the platform. 
The topmost level is almost completely rectangular so the kit part needs to be cut down and the gaps in the sides filled with some more small rectangles if stainless steel. Note the mast is different and supports the square SK RADAR, not the round SK-2 carried by Missouri. Finally note there is a 20mm gun in the tub just forward of the Mk.37 directors abreast the funnel, so remove the stump that is supposed to be a rangefinder in preparation for this.
The rear structure has other minor differences, notably in the positioning of the rangefinder tubs. The third and uppermost tub above the three 40mm emplacements should be deleted, as should the extra two tubs just below the range finder position. 
The two tubs on the sides of the funnel should be separated and placed at opposite ends pf the funnel as shown and the gap left where they would have otherwise been fitted filled. Note that in the small tub protruding below the three 40mm emplacements Iowa carried only two, not three 20mm guns so remember this for when you come to attaching these.
All the armament (20mm guns not shown) was built and painted while attached to the sprues. The only things to note are that Iowa carried three 20mm guns on top of B turret instead of the 40mm quad mount. The shield was made from railing but the gaps filled with paint to give a solid shield. C turret was enhanced by adding the rangefinder tub for the 40mm mount, made by bending a rectangle of stainless steel.
You are probably wondering by now when I’m going to pain the ship. The answer is now. I thinned some of WEMs 5-L and sprayed the whole ship with two coats. The reason I wait until this stage ins because it means I can paint all the major photo-etch and most of the ship in one go rather than fiddling with subassemblies. I then masked the camouflage and painted it 5-N and then, with a very small brush and very carefully, I painted the decks 20-B by hand. See images 18-22 below for the ship at this stage. Note the 40mm guns have been attached, but the 5” and 16” guns are just sitting there to make the photo look good. I will only glue these on after I have finished other details.
For the final detailing I painted and weathered the PE doors and fire hose racks separately then attach them to the ship. The same goes for the 20mm guns. I used watercolour washes to weather the ship slightly as well as a pencil to lightly highlight detail or create smudges and traces of water on the hull. And now for the railings. The main deck railings were attached to the ship unpainted. Again I used a small brush to pick out the stanchions in the relevant camouflage colour and then used my black permanent marker to ill in the horizontal bars. I do this because it keeps them thin and gives the correct impression that the railings are cables through stanchions, not solid bars. The upper railings however were all painted 5-L before being cut to the correct length and attached to their correct positions on the ship.
Finally, the flag decals from the kit can be attached and the rigging made from stretched sprue. A little dilemma was how to convert the “63” decal to read “61”. I hit on the idea of attaching it to the ship then, once again using my trusty small brush, paint the horizontal portions of the “3” in the background colour leaving only the vertical part which resembles a “1”. 
I hope that was a useful article for you, especially if you wish to try a conversion yourself. If you have any queries you can contact me via the forum on this website.