[Mixed76]

A word of caution - halon, CO2, and other gaseous fire suppression systems are designed for enclosed spaces where they can exclude most of the oxygen in the vicinity of the fuel. Not saying they won't work on a small fire but you might need a big extinguisher to keep the air out of a large enough area to extinguish a fully developed gasoline fire, or where there is a breeze, fuel is going under the car, etc.

Powder exchangers work well on fuel fires and are pretty efficient for size. Yes they are messy, maybe preferable to a total loss? Premixed foam/ water works very well on a pool/ puddle of fuel or a limited spray area. They can be heavy, dunno if available in a useful size?

Main thing for any of these fires is to stop the flow of fuel, or for an electrical fire, stop the flow of electrons as Chris B. pointed out. Stopping the flow of electrons also eliminates a source of ignition so the fire doesn't relight.

Electrical fires in old 911s are generally going to be limited (as Walt pointed out) by the relative lack of combustible material; wiring insulation doesn't burn very well (as designed) and the energy source (the battery) isn't very large.

It's gasoline you want to worry about. As everyone says, make sure your fuel lines are made of the right material, are reasonably new, and aren't subject to pointy bits/ rubbing on surfaces or edges. O-rings should be fuel rated, connections tight, etc. Battery cutout to stop the fuel pump and ignition sources.

I carry 4 lb ABC dry powder extinguishers but have not installed battery cutouts.

Source: I spent >10 years designing fire protection systems for mega oil and gas projects. Offshore the main system is enormous quantities of pumped water and foam; onshore you have that plus very large powder or foam and water fire extinguishers on wheels. Halon/ CO2/ FM200 is only used in electrical or instrument rooms.