Hi Dan,
Very happy to share thoughts. My vehicle is a U1550l37 already fitted with turbo and intercooler. Benefit as I see it is that I will be able to maintain a modest pace when I hit gradients and not be too much of a pain to following traffic. I'm happy with 55mph and so not too worried about fast axles.
I don't have experience with these before, but have had a past of upgrading drivetrain in race cars and the issue with doing stuff like changing portal ratios could be that you need to think about every other link in the chain to eliminate weak spots. (In race car terms increasing tyre size or switching to slicks required upgraded uprights, drive shafts, diffs, etc etc. )
I'm swapping the standard tank for bigger. One of our goals is long bush trips in Australia and Africa so extended range is important. This also leads to considerations like water filtration etc.
I started building the body at the weekend. I'm building an al frame with foam composite panels.
I'm tall and so am lifting the cab roof by 20 cm. I will have a roof mounted centre console for radio and other cab related stuff.
I'm properly stuck on insurance though. I'm having zero luck. Given my build will take a couple of years I'm beginning to be resigned to sticking the truck in a shed until it's 20 years old (15 months) and then getting vintage cover.
I've tried every phone number I can think of or Google and I'm at my wits end at present. It is crazy after 30 years totally clean driving including some fairly "capable" machinery that it's so difficult to get cover.
Let me know what you're doing - it's always good to have someone else exploring the same stuff.
By the way, get Uli Dolde's book, it's super helpful.
All the best
Nathan