No, I haven't seen a 6BT in any Advance Design or earlier GM truck either. Someone's got to be the first (And at my pace, it likely won't be me). I haven't measured a Diamond T engine bay, but at least within the 1-1/2 to 2 ton size range, I think they are somewhat similar in size and shape to Chevy/GMC engine bays. So I was suggesting that if it worked for that guy, then it should work for us.
Is it worth it? To me it is, but I'm building my truck because I like doing the work. I would never recoup my time investment if I were to sell it. I'm building it to be an extremely capable truck--to use, and to tow, and I'll keep it for a long time, possibly forever. So for me it's worth building what I want. But, I certainly don't have to convince you of that..... hehe.
Bob