3-4" extended cab photo shop?

[Hawssie]

The 67-72 trucks have always been my favorite body style of any truck. It was my first truck back 82. But in my late 20's I screwed up my back and never was able to get comfortable in the rather small cabs of these trucks. I am also over 6' tall. Because of this I moved to the Blazers and still have 2 of these. I just got through building a 1970 c10 for a family truck and I am now going to do a 67-68 and it brought back an idea I had a while ago. And that was to extend the cab maybe 3 inches. The least noticeable way I think would be somewhere through the middle of the doors, cab and roof. The frame doesn't matter because it will have a custom frame and front/rear suspension anyways. It would be a lot of work and would require custom door glass and panels,carpet etc. I think 3 would be the most before it would become strange looking. I was wondering if anyone had seen this done or had any input or maybe could photo shop a truck so I could see what it would look like. My reasoning again is not to make it look different but to add more leg room, and do you think 3 inches would be worth it? Maybe 4 inches?