Apologies to hijack a great build thread, I agree the benefit depends on how you utilize the truck and there are several good threads discussing.It's a fantastic mod. I'd put it up there as my #1 or #2 modification.
Detailed discussion and installation here
For me it is a great mod for how my 200 series is used, a large amount of driving concentrated in somewhat remote parts of the West where fuel locations are scarce and can vary in price.
A 450 mile range is a lot more convenient than 280 when you cover a significant amount of territory, whereas a truck that largely operates in or near the cities is just fine without it.
