Driveshaft is the least of any problems. I would not be concerned there. Lots of places make custom drive shafts for 4x4's. And for steep angles very common on trucks you can get cv joints instead of Ujoints.

I have driven large 7 pax vans in Europe with a 1.9 TDI in it. No problems what so ever pulling it around.

Hood bumps are easy to make.

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77 300D- new to me, lots of "issues" to deal with. But a nice unit.
Diesel man- 84 Toyota Diesel cruiser