I ran a vortech (a centrifugal supercharger) on my old explorer (1991) 4.0 OHV. The OHV is not as much of a high RPM motor as the SOHC , so take this for what its worth:
I can tell you that while it was great under boost, I didn't get into any significant boost unless I really got on the throttle (floored it) and got over 4000RPM. Normal driving (part to mid throttle) would never get me into boost. I would think that an M90 (positive displacement supercharger) setup would be better for these heavy trucks since max boost comes up sooner in the RPM range and you would then get the power and torque starting lower in the RPM range...a heavy truck such as ours would really benefit from power and torque lower in the RPM range.
On the other hand, if your driving style or intended use for your truck is more of a street/strip application where wide open throttle situations are very common, you might like the vortech since it gives you all that power up top.
All I can say is that the vortech, while a good unit, was kind of like driving a turbo car with a huge amount of lag. Didn't see boost from 0-3000 RPM but when the boost came in it was very noticeable.