BTW - Here's an aftermarket solution for AWD for the F650, without adding ride height:
https://eztracawd.com/ez-trac-product-information/Factory 4x4 on the International might put the frame rail height out of reach of most 5th wheels. The weird thing is I can't find any actual specs on the 4x4 versions, much less a real picture. All the "pictures" of the 4x4 versions on their website look like renderings... So it makes me skeptical that they represent actual ride height. There's only so much you can do with a solid axle under a straight frame....