Difference Between High Output And Normal Alternators?

I've been wondering lately about the main differences between high and regular output alternators. What exactly enables the alternator to make more current? It doesnt seem like the windings are that much bigger so is it just a stronger field coil or bigger diodes, or maybe spins faster? If anyone can enlighten me on the subject i would appreciate it because looking around online just gives me basic explainations of how alternators work in general but nothing specifically about high output alternators. The reason that got me wondering was i heard there are some stock alternators that can be upgraded by swapping the core with a "bigger" core. And ive seen where cars that share a body style/platform like a mercury mountaineer, for example, will come equipped with a 160 amp alternator and a ford explorer might just have a 90 amp alternator, but the outer shell is exactly the same. So it shouldn't be a matter of bigger physical size. Thanks in advance