You can pretty much see my complete build here
http://www.pirate4x4.com/forum/expedition-vehicles/933305-f-700-4x4-camper.html
Make a new roof cap? It's more work but your work is nicer than the factory stuff and sometimes by the time you are done fiddle farting around and it's not making you happy you will be done a new part with the correct fit. Make it 1/8" cock eyed the right way and all is good! There is a great build on this forum on Mike Hiscox' Earthroamer, the renovator did not use a tape measure or square to fit any of the components and it turned out pretty nice considering they were taking somebody else's problems and making it right, looked to be the process when the world isn't perfect.
My truck is equipped with a 5.9 Cummins, great little motors that can! I have had a lot of interest regarding building custom campers stem from my build, I did a frame up on a newer Peterbilt for one fellow already, quite a few requests from the Dodge 5500/Ford F-550 camp, lots of people identify the shortcoming in the RV market. Might make a nice little retirement business or maybe even a semi retirement expansion of my current business.