Just thought I'd post my findings because I really couldn't find any hard facts as to how much these rigs consume. Of corse there are several variables based on setup and equipment, and trail but.. this is what I found after running my rig on the Rubicon for the first time over the weekend.
Here's my setup
84' Pickup Bobbed Bed - Loaded with 2, 10 gallon tanks 1- 8 gallon tank and all my camping gear, spare parts, tools etc.
Dual Transfer cases, stock gears
Toyota axles, w/5.29 gears
Bald wornout 35/12.50/15 tires
newly built 20r/22r hybrid engine.
Of course GotPropane Kit
I ran from buck island to the Loon Lake staging area, in 6 hours.. very few stops. Hand calculated (by tank weight) I burned 4.4 gallons of LPG!