Whitearrow,
I'm presently using two plastic barrels, a 30 gallon and a 20 gallon.
I purchased a 12v Tuthill Fill Rite pump, and fitted a waterblock filter to it. I hooked the leads up to the aux terminals of a 7 pin RV trailer plug, and can power the pump directly from the hitch connection of my truck, or to a battery by using a separate female connector with clips. Clearly, I didn't need a 7 pin, but it was the only configuration that could be wired directly into the plug with the factory conductors. These 12v pumps pull some serious juice, and any molded trailer leads were too small a gage.
I'm supposed to wire the clip connector directly into my JD 4120, but haven't found time for that yet.... Too busy digging!
I bought my pump new on e-bay, but they are available readily from Northern Tool as well as other vendors. Picked up the filter from TSC, who also carries pumps - just not Tuthill. I think Great Plains is the name of their line. I should add that TSC also stocks rebuild kits for their electric pumps if parts availability is a concern.
I've been using this setup since November '05 and it woks great. I'm constantly on the lookout for a used skid tank or a 275 gallon oil tank, but haven't found one yet. I've been getting the drums filled when I get #2 oil delivered, but we're talking the heating season here. I don't think he'll come out to drop 50 gallons.
I'm gratetful to TBN member Anthony (from nscale monster trains) for this setup idea. I did however, use connectors more suitable to my circumstances.