John, check the detail differences before you begin. there were changes, even on the E3, which need to be checked against the specific aircraft you wish to build. For example, in the last drawing posted, which I posted in another thread, you'll notice that the propellor pitch control was moved from the centre of the instrument panel, and this was blanked-off, being replaced by a switch on a re-designed throttle grip. The earlier grip was a 'ball' type.
But, it's possible to find an E4 with the earlier grip, and an E3 with the later grip, and so on, due to upgrades, field modification packs etc.
A good example of this is 'White 4' of JG26, now preserved in the Imperial War Museum, Duxford. At first glance, it appears to be an E3, the main feature of this being the earlier 'rounded' canopy. But in fact, due to some engine and electrical fittings, and other upgrades, and from the factory plate, it is an E4 !
A number of kit manufacturers have based their kits, and the cockpit in particular, on a particular existing airframe, or sometimes just a photograph, and this leads to pitfalls for the modeller, although fairly minor ones to be fair. A typical example of this is the inclusion of the small ETC switch panel on the lower instrument panel, which was only fitted to bomb or drop tank equipped 'Emils'.
Another point to note - it's generally accepted that the cockpit colour of the 'Emil' was RLM 02, which is the colour 'officially' stipulated for aircraft interiors of the period. However, on the ones I have seen close up, or have seen colour pics of, and when examining contemporary pics, even in B&W, it is evident that the colour isn't actually a true RLM 02. It seems to be in between this and RLM 66, which replaced 02 as the interior colour, and is more of a mid, to dark grey, with a hint of green, though not quite as dark as RLM 66. It's a bit like RLM 75, with green in it!
Sounds confusing, but the easiest way to describe it, if you are familiar with Humbrol paints, is Humbrol 27 Grey (basically RAF Ocean Grey) with a couple of spots of Green 30 (RAF Dark Green equivalent) and., depending on scale, maybe a small spot of white to lighten it slightly for 'scale effect'.
Hope this helps,
Terry.