[Zoomad75]

I really hope you a packing a truckload of cash to go with the duramax. I'm not trying to discourage you, but it's not a simple swap. First you got to choose what vintage of d-max to pull from. Early ones have the injector issues up to mid year 04. Later ones got EGR and starting in 07 they started running the Diesel particulate filter. If you run the later one, you either need to integrate the emission garbage or find somebody that can tune the crap out. I wouldn't even look at a 11 or 12 d-max for the fact that they got saddled with the joy of needing diesel exhaust fluid (fancy name for synthetic urea) to even run.

Next up is transmission choice. The obvious choice would be the Allison 1000, but they did have an option of the ZF 6 speed manual trans back in the early years. Problem is either trans is physically massive in size. Either trans is very tall. So tall that the 3/4 and 1 ton trucks this engine came in have much taller frames compared to the 1/2 tons to help cover everything without need for factory body lifts. Fitting in a 67-72 would require a body lift and or surgery to the trans tunnel.

You are on track with going to the driver side drop on the t-case and front axle. That means you are going with a push button t-case. Add more complexity with a t-case control module to run that stuff. That is unless you can put your hands on a manual shift t-case from an earlier version.

There are ways around a lot of the issues, most of which comes back to money. I'm not saying it can't be done, but it won't be a budget build in the least. Good luck with it!