This might sound strange, but looking around the house for something to work with, I found a piece of aluminum that has "fins" on it lengthwise and it was hollowed out already....it was from when I put verticle blinds up in the house and had to shorten it. You can buy an 8foot blind for $22 for the top rail an dull the "aluminum dowel" from it and have enough to make about 40 of these coolers.
As for the chiled fuel...I used to run this in my nitro oval car, because we were hardly ever off the throttle...be careful as to not keep the fuel too cold, as this can cause signifigant engine issues. Just keeping it 20 or 30 deg cooler is all that is needed. When you get cooler than that, after refueling, I've seen guys that have fractured pistons and had bearing failures.