i used 8ga on my truck, alt b+ runs to the lug on the relay, then from there i feed into the cab bypassing the bulkhead (coz it was melted at the terminals). used 12ga fusible wire as well.
ordered one of the repro Denso style alternators, just looking for 60amp output, the test sheet shows the alt puts out 120amps at 13.5V...hope my 8ga wire is ok.
Actual output from battery or alternator depends on the load.
In other words, whatever items are using electricity are primary determiner.
The second determiner is the voltage at which the items get the power.
For example, if power is provided at 14 Volts while the engine is running.
Ignition and field need 4 amps (1960s ignition and alternator)
Headlamps and markers draw around 12 amps
So driving at night, the alternator output would be 16 amps.
The only danger of a high output capability is if the battery is run down.
Batteries will draw current for recharging in proportion to the charge state.
A fully discharged battery, offered power at 14 Volts, may try to draw 40, 50, 60 amps or more!
Most of the factory alternators in the 60s and even 70s couldn't provide that, at least at idle, so the system was somewhat self protecting.
