One other thought, for those of you without side curtain airbags but WITH rear A/C. If you get the barrier that is shorter to fit under the rear A/C duct tunnel, you may also be able to fit it under the sunroof in the forward position (behind first row of seats). Normally, Milford barriers can go into two positions, as Hugh states: either behind the second row if you need to carry passengers, or behind the first row if you remove the second row seats for more cargo room. However, for trucks without rear A/C, the standard (taller) barrier will not go into the forward position because the sunroof assembly gets in the way. But if you buy the shorter barrier designed for trucks with rear A/C, it may fit there. The reason I say it will only work if you don't have side curtain airbags is because the upper mount points for the forward position bolt in right under the grab handles above the rear doors. Since this is where the side curtain bags resides and deploy from, you obviously don't want to be drilling and mounting anything there!
But better check with Jim at Midwest Land Cruisers (distributor) to be sure about all of this.