I haven't fallen in the drink just yet. from time to time I have to go a train noobs no how to "flash" update a cars onboard computer. these two just were not up to the task.
In a nut shell E's 1 thur 3 were all the same. E-4's were still E 1/3 with a uprated 20MM in the wings and added armor around the fuel pump/tank and pilots head. E-5/6 were recon mechines. and E-7/8's were E-1/4's with added bomb/drop tanks. The luftwaffe just kept updating the old E's. These aircraft even kept there same work #, they just carried the new sub varient number. Some "new" E-7/8 were built but not many. As mentioned the spinners had a few differences depending on engine armerment. Trops or sever duity E's only differed in having the trop filter and some could of had slightly larger tires.
There were changes internal to oil,cooling, and electrical systems but these were not detectable by outward appearance. So basically if you have mechine guns in the wings it's an E-1/3. 20mm E-4. A drop tank or bomb rack E-7/8. Cameras installed E-5/6. because of constant upgrading you can easily have an E-1 that now has 20mm's and a drop tank, thus the equiptment tells you what time period you are looking at.