Do not cut the tank with a torch or plasma cutter without purging with inert gas or filling with water. The heat will vaporize remaining liquid and create an explosive atmosphere inside the tank. Only use a sawzall if you can have someone keep soapy water on the blade the whole time you are cutting and a slower speed with good blades. This way no heat to vaporize the fuel. Oh a co2 extinguisher can be used as a purge gas if one is laying around plus nitrogen or argon will work also. Good luck..................