Both our trucks have garden trucking 3" extensions. When you get them, they come with dimensions and pictures of where to cut. They fit very snug and solid. Just make sure you have a perfectly square cut so the seam is less noticeable.
It is a lot more work like Dabears said but it's better than having to drill and tap a whole bunch into custom rails
If I recall correctly, it's 1 1/2 inches back from the back sleeper hole is the cut?
I can take some close up pics if you'd like.
I think the globe on king rails looks perfect in the pics posted. When I build my first globe, it's gonna be on a kinghauler frame for sure! Thanks for sharing guys
Mario