what is the capacity of the seat tanks on the 61 GMC pickup? I have been driving it the last 3 days. running about 120 miles a day- averaging around 10.8 gallons a day. the old 305 is thirsty but it keeps going and going.I'm holding it around 60 to 65. every day was a bad headwind on the return run. 2 days really bad dust storms with it.if I can get the play out of the steering box to where I don't have to herd it so much I'll feel fairly comfortable except at the gas pump.get lots of good comments anyway.