I used 3/8"OD aluminum hard line for my supply and return lines, it's something like $1.50 or $2 a foot, and you'll need 10 feet or so. For heating my fuel lines and tank I used coolant hoses bundled with my fuel lines, and I had a coolant tube welded into my tank and ran coolant through that which kept the tank from gelling up. Never had any issues. You don't heat to heat the tank a ton, you only need to keep the VO liquid and flowing easily. Worry about cranking the VO heat up in the engine bay.

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