Greetings....from N.C. I have the E 350 (2008) 6.0 L with the QUIGLEY package. My second 4x4 van and just want you to know who you use to get your 4x4 parts.... is just as important- as who you get to install it.
Ask ten people..you might get five or ten different answers. If three or four are similar...then you got it narrowed down. Most older RV owners do not care about rock hopping or doing stupid things with their 4x4 RV but do want to know they will get them out of trouble...when trouble actually occurs. All depends on ones perspective. Ive crossed the nation many...many times...and gone deep into Canada and deep off the grid in good backcountry roads. Like the old scouts....BE PREPARED.
Go cheap...and break down...go with an experienced dealer and mechanic and it'll be right for as long as you keep your mantaince up.