These old car's electrical systems were NOT designed for high current draw devices. IF you decide to add all kinds of loads I would recommend you add a power tap / buss bar to the alternator output and then run all your loads off of that., You will need an ignition switch controlled relay with sufficient current caring capacity to control buss bar.
Also the stock output from the alternator goes into the car through the bulkhead connector (prone to overheating, melting / catching fire) then to the main splice (where most of the car is powered from) then to the Ammeter then back through the bulk head on another connector, then to the starter relay post then to the battery. There is a By pass called the MAD bypass that will eliminate the bulkhead connectors and the ammeter.
The reason to bypass the bulkhead and ammeter is while the engine is running the current coming off of the alternator output is the perfect source, but if all that load is on and you shut off the engine then all that load must be powered from the battery. that means it all has to go through the path I outlined above (but in reverse) and the wiring is not up to the challenge.
