Mysterious to me at least... I'm sure to the Beierl's of the word it makes
perfect sense!

The alternator led circuit has me confused.  (This is shown, for example,
on 97.74).

It goes from 12 volt power supply, splits into two tracks.  The first track
goes through a 60 ohm resistor, the second track goes through a 470 ohm
resistor and then through the alternator led, and then they meet up again
and go through a diode on their way to the alternator.

(The 60ohm resistor is actually two 1watt 120ohm resistors in parallel).

Why does this need to be like this?

My curiosity stems from the fact that I have two 1 watt 100ohm resistors
available, and I'm wondering if I can replace those 25yr old 120ohm
resistors with them, or if I need to leave them be.  I'm also wondering
what parameters I need to worry about from the standpoint of upgrading that
LEDto something brighter.