Jim,
If your looking at the height that your hitch needs to be, the flat top of the hitch in the truck should be around 46" from the ground. With that said there is approx. 6" of adjustment with in the pin box itself. The suspension does have about 4" of adjustment in it.
I adjusted mine, my self when I first got it and I was pulling with my F250. After getting the Volvo, I change the pin box to a Trailair pin box and also needed to adjust the suspension to get it to ride level. I do not have the Mor/Ryde IS suspension but I think it is adjustable also. Look at their web site to make sure.
Jim here's a link.
http://www.morryde.com/pdfs/IS%20OWNERS%20MANUAL.pdf