If the amperage draw is close to what the stock components can draw, I don't see what difference it makes to the ammeter as to what output the alternator is capable of.
Correct. Under normal uses, it doesn't make a difference.
In fact an alternator that can keep up with high loads even when the car is stopped will be easier on the ammeter and battery feed.
That said, batteries will draw more current as their charge state decreases.
For example, a battery that has just started a car will draw 15 amps from the alternator for a few seconds, then 10 amps for maybe a half minute and the current will continue to decrease until its practically zero five minutes later.
But a battery that has been discharged by accidently leaving the parking lights on for 5 hours will be another story. If the engine has been started with a jump, and is now running at fast idle, the battery is going to be very hungry and draw 45 amps. Now if the maximum the alternator can produce at 14 Volts is 40 amps, then 5 will go to the ignition and field, that leaves only 35 amps to go through the ammeter to the battery.
