No doubt the E-Series has narrower doors than the F-Series, but pictures show that doors on E-550 were the same as on E-350 and E-450. I would guess that to clear the larger tires Ford raised the front end a couple of inches, but I doubt that would be a major issue for most buyers since they come with a step at front doors. Most RVers report they like to sit high anyway, so that may be a plus.
Some of the Internet pictures do make it look really ugly, particularly the entry level work trucks with dark plastic bumpers and wheel flares, and steel wheels without hubcaps. In my opinion E-350s and E-450s in same trim look pretty ugly too.
What I think is most important is that if Ford does offer an E-550, that they use a stronger and stiffer frame, and offer it in much longer wheelbases. Motorhomes requiring the GVWR of an E-550 will likely have wheelbases over 200 inches in length. They need longer wheelbase options like on F-550 and F-53 chassis.
I agree basic work trucks were ugly:
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