I went out in the driveway and measured three E250 vans for you:
This measurement was from the step on the passenger side door to the floor.
1: Stock E250 with 245/75R16 tires (tire height 29.5") was 21.25".
2: E250 with 3.5" front lift, no rear lift with 245/75R16 tires (tire height 29.5") was 23.25". (This van sits very low in the rear and will be getting a 3" lift in the rear before it is done.)
3: E350 with 3.5" front lift, 3" rear lift with 285/75R16 tires (tire height 31.75") was 26".
Subtract the radius of each tire (van sitting on the axle center line) and you get the following:
1: 0" lift at the door step (it is stock).
2: 2" lift at the door step, with just a front lift.
3: 3.625" lift at the door step with front and rear lift.
You can see that tire size makes a big difference until you normalize everything. So does the "personality" of each van.
You can extrapolate from here.
I hope this helps.