Yes, Winnebago lengthens various Ford chassis on many of their models. They even used to shorten certain high GCVR Ford chassis to get the capacity they wanted on a shorter coach but not sure there are any like that right now.
Ford has guidelines on how to lengthen / shorten that Winnebago follows. They have a chassis shop with laser alignment equipment in Forest City that does it.
Randy - Manhattan, Kansas
2015 Vista 27N
2016 Honda HR-V
Just as a For What It's Worth comment:
I'm just old fashioned enough to not trust anyone but Ford on how to construct/mess-with one of their chassis including install a longer driveshaft that will never vibrate.
I don't even completely "trust" the small extension that Winnebago welds onto the end of the stock Ford frame so as to provide a trailer hitch. I have to live with that on our small Itasca Class C ... but don't tow anything heavy with it, either.
So if you get under your rig. And look at the frame. You will notice that the frame was cut and extended 3 or 4 feet. They weld in a piece of channel to do this. The welding job on ours is scary as heck. I was a welder for many years and we called welding like that bird **** welds. Because it looks like bird **** instead of a good smooth weld. One side is perfectly welded the other side looks like a beginner did it. But lifes been long and if i go out because of a winnebago welding job. The family will be taken care of after the lawsuit.