Because it is a 2000 Expy, it is AWD. All 99+ trucks went to AWD and as I recall there are no 2wd versions out there. So, that means the truck has to be AWD, therefore torsion bars on the front end.
As for doing the torsion keys and then cranking them to the max, you are really going to be stressing the lower and upper ball joints on the front end and putting them under a lot of stress. Not to mention that you are going to have really bad feeling in the suspension as you are going to have no downward wheel travel. So, any pothole is going to result in a tire leaving the road surface. Not sure about you, but that is bad in my book.
soulatlamour, why do you think you need that much more clearance. The only way that you are going to get that much more clearance is to run a 37"+ tire. To do that, you will definitely need torsion keys, rear coil spacer, and a body lift to fit tires that size (37's will just fit, with some additional work). But, I think you will find that going with 35's and a body lift is going to be your best way to get the additional height and keep things on the cheap. Please keep in mind that I only recommend running 35's if you have the stock 3.73 gears. If you have the stock 3.55 gears, then you are also needing to add in the cost of a gear swap. If you are looking at 37's, then a gear swap is a mandatory thing unless you want to rebuild your tranny here soon. But, that is an additional $2000 for the new gears.
Keep the questions coming. If you want me to explain my point about the ball joints, I will see if I can find the posting I put on another site where I got into the science behind the angle of the ball joints and just what the ball joints can take.