Yes- the PowerTank in the large size (we'd call them an "80" in the scuba days) are pretty awesome. I wanted to see what the capability was with mine the last time so I just used it as much as I wanted to- I shared with my friend who was driving with me (his crappy little Autozone pump was so slow) and I didn't ration it at all for 3 weeks. Like I said, there was still usable gas in there when I came back. I'm sold on it but I will say that it is heavy and does take up some space in the bed of the truck- also, if you can, opt for the 1/4" ID uncoiled hose the standard set up comes with a coiled hose that is really compact but if your tank is in a set spot and you have to stretch out the hose, it can get kinked and tangled- it's good, not great. I now have 30' of straight hose for my rig.
The through Lake Chapalla is really pretty too- and it's going to be paved completely in another few years. Your rig is killer, you should head down!