in the reference pictures, the tank was made with very simple geometry and then just textured.
all the vent type stuff and headlights on the front is just a texture on a flat poly surface.
you could maybe give it a small bump map to make it look a bit less flat.
but if you're trying to make a high res/high poly, fully modelled version of that then the way you are doing it is the best bet
all thoes edges that you have spanning the middle of the tank you can just delete thoes.

if you were say making a smooth car you might maybe wanna keep thoes edges, but since this is a very flat, very rigid metal type tank you aren't going to smooth the gemetry so you don't need to carry thoes lines the entire span of the tank, you can easily get away with 5-6 sided polys and should have no problems.
this method you are probably used to for the modena because it has such a smooth body and so many body lines to follow, so its a smoothed object, but this one you can render off rigid like that in low poly mode and it will look best.