I think what these guys are are doing is dropping the voltage to the alternator's "sense" wire. That wire goes from the battery to the alt's regulator to tell it what the battery voltage is (which is how the alt knows how hard to work). If you can make the alt see a lower voltage than what's at the battery, it'll charge harder to compensate. That GM part number comes up as a diode (not a fuse), and the Arclight product looks like two diodes on a circuit board. Diodes have a forward voltage (typically 0.6-0.7v), so I think what they're doing here is adding those diodes in line with the sense wire, causing the regulator to think that the battery voltage is lower than it is. If this mod works the way I think it does, either the GM diode or the Arclight on its low-boost setting would give you a 0.6-0.7v increase at the battery, and the Arclight's high boost (which I assume puts the two diodes in series) would give you a 1.2-1.4v increase at the battery.
Comparing the output voltage spec in the '03 R50 manual (14.1-14.7v) to the 4Runner output shown at the start of the first video (13.6-13.7), it looks like the 4Runner owners are doing this mod to achieve the charging voltage that yours already makes. Century's website suggests 14.6-14.8v, so your charging system is probably right about where it needs to be already. If it's towards the low end of spec, you could probably boost it using the same method (looks like the R50 has a conventional alt and the same 7.5a fuse on the sense wire), but if it's working now, it's probably not worth messing around and potentially boosting it too far. Worst case (high end of spec plus an Arclight at full chooch) would be pushing 16v. At least the Arclight has a fuse, though--as clever as the GM diode mod is, unless that diode happens to pop at around 7.5a, that circuit isn't properly fused anymore.
As an aside, why do people making Youtube videos think they need a backing track while they're talking? And why does that one sound like an ice cream truck with something wrong with the cassette deck?