I was thinking about getting one of the Harbor Freight 1" clear water pumps and using a small (400 watts or so) 12VDC-110VAC inverter to run it.

These pumps are the same ones that so many folks use for circulation and transfer pumps for their bio processors. I'd think they'd be up to the task.

Another option I'm considering is the 500 pound winch-operated lift Harbor Freight sells. It fits in your reciever hitch and has a 2'x2' lift platform that will lift 500 pounds up to the height of your tailgate. They cost a couple of hundred bucks, but you could easily load the whole barrel full of oil into your truck and leave an empty in its place. No need to pump the oil out of the barrel until you get it home.

I picked up one of these lifts at a garage sale with a busted winch for $35. I think I could pretty easily replace the broken winch with one of the 2000 pound utility winches that Harbor Freight sells for $49 (the ones that are power-in / power-out - NOT the phony one with the mounting plate that hooks over your hitch ball) and get the lift operational pretty easily. Then I'd just get a few "spare" oil collection barrels to swap for the full ones and be in business....