I did this, however, all of my vac lines were in decent shape, so I just unhooked them from the T-case and re-routed them into the cab and up to the dash. Also, I used a rotary type valve, 1/4 turn of the knob locks/unlocks the disconnect. I left the vent port on the valve open behind the dash, so I get a cool "shshsh" sound when I turn the knob.
One thing I have noticed though, you need to either be sitting still, or have the T-case already in 4wd, before you engage the axle disconnect. If not, you'll get a "bang" when the axle engages and starts to turn the drive shaft.
even if you don't have a front locker, this mod gives you the ability to have 2LO, which I find that I use quite a bit for moving the trailer around the property.
maroon 1987 Grand Wagoneer. stock for now...