Removing the petrol tank is an awkward and dirty job. Most of the securing bolts will be corroded and siezed. if so they have to be cut off.
One common source of problems is the steel pipes coming out of the top of the fuel pump. They are sometimes corroded so badly they collapse into a pile of dust. If this is the case, the fuel pump assembly must be replaced. In addition, the fuel pipes themselves are often badly corroded. They have to be bent to connect them to the new petrol tank with pump installed and often do not survive this. If so, they must also be replaced.
When the reserve petrol tank has been fitted the toroidal LPG tank can be fitted in the space freed up by removing the original petrol tank.
The boot floor must be reinforced as it is not strong enough to bear the weight of a full LPG tank.

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