I'm interested to know what you think of those tires, Michael. Always appreciate it when companies get "real" people to test their equipment outside of laboratory settings. Good for the consumer, and good for them.
As a photographer who has used all manner of gear - everything from 16mm Bolex movie cameras to a Sony A7R, to a Linhof 4x5, the 5D MkIV and MkIII are both solid cameras, and in my opinion some of the best Canon has ever built!
For us overlanders, where space and weight is often at a premium, I can't recommend adapted lenses enough. There are a lot of situations where autofocus just isn't necessary (e.g. landscapes, photographing stationary objects). Manual focus lenses are often much smaller, oftentimes lighter, have better build quality (all metal construction) and if multicoated, usually at least as good if not better than modern autofocus counterparts. (You can determine if the lens is multicoated by looking at reflections on the lens - if there are 2 or more colours, it's multicoated).
You can get some very good classic lenses for little money on eBay if you know what to look for (just make sure there's an adapter out there that'll fit them. If you're buying from eBay, I've found Japanese sellers with lots of feedback to be the safest bet; good prices, and the quality advertised is the quality you get. KEH, online but based in Smyrna, Georgia, USA, is also a great option.
Manual Nikon lenses fit digital Nikons as well as Canons when an adapter is used. If you want something a bit pricier, but with phenomenal quality Leica R-series lenses are the best in my opinion! For inexpensive yet quality glass (often made by Zeiss!) M42-mount lenses can't be beat. These will mount on Canon DSLRs, and there are hundreds if not thousands to choose from. It's a standard mount used by a bunch of different manufacturers. If you're really into adapting lenses, Sony mirrorless cameras can take virtually anything out there. I also like them because the bodies are smaller; I keep my A7R stuffed in the glovebox.
http://allphotolenses.com/lenses.html is a great site for objectively comparing different lenses!