Get that fire extinguisher recharged, if it’s rechargeable; if not, get a new one. The seal on the extinguisher will leak after it’s used, and you’ll have no pressure if you ever need it again.
You should rebuild the carb to replace all the gaskets, but fires need both a fuel and an ignition source to start – did you have a backfire through the carb from the intake manifold? Check your ignition wire routing (specifically #7 and #8) to make sure you don’t have a situation where crossfires are encouraged. Also check the condition of the plug wires in general, and if they’re old or if you recall ever hearing snapping sounds under the hood when the engine is running, then replace them.