This regulator will work just fine if your primary objective is the ARB. ARB recommends 80 to 100 PSI and PowerTank recommends 75 to 90 PSI for the ARB. I am running 90 PSI to my front ARB. PowerTank claims you can get over 200 actuations of the ARB per pound of CO2. I don't use it for air tools, but paid the extra bucks for a PowerTank regulator just so I could some day if I wanted. They have a very compact regulator that used to fit only on the paintball tanks, that they have adapted to the threads on a large bottle now. If you plan to use air tools, I would worry about this regulator iceing. As suggested previously, you could probably find a better price for this or equivelent quality regulator.
I have a 4 pound tank, because it fits against the rear wall, where I removed the spare tire mount bracket. I chose this size tank because it is as wide as the wheel well, so it does not intrude into the main cargo area. I ran the air locker for 10 days in Moab and still had enough CO2 left to take eight 10.5 x 33 tires from 12 PSI to 25 PSI at the end of the trail. I got back to NY with 600 PSI in the tank.