[Accelo]

My current truck has a driveline speed of 6000 rpm at 140 mph in drive.
I know this because it was dynoed at this speed.
I have a factory short box that was originally built with a two piece driveshaft.
Now it has a one piece shaft in it's place. My driveline was designed by an OEM not me.
Considering a long box truck would have either a 12" or 18" longer drive shaft it would be up to them, and their intended usage, to decide it a one piece is the better idea or not.
Four wheel drive trucks typically do not have the same issues as the transfer-case shortens the driveline length requirements.
Converting to an overdrive transmission will typically shorten the driveline length requirement by two to three inches.
So the drive-line in my truck is almost 3" shorter than if it was a stock THM-350.
Larger diameters are safer and less likely to clear the hole in the frame.