Know that the code 8-39-0 refers to the LAMP which is a bulb and socket
assembly.
The bulbs by themselves are listed by part number crossed referenced to bulb number in section 8-44-0
High Beam Indicator bulb is part number 127 934, which cross references to Bulb # 57. It's used in many different applications including Monaco and Polara USA versions, for everything from Gear shift selector to turn signals, heater controls, etc.
However, in my experience, some of them may have switched out to the wedge style bulb and socket with a bulb number 158. It depends on whether the high beam indicator is powered from the printed circuit board (which would use a # 158), or is powered by a wired socket like the turn signals (which would use a # 57).
Often times the connections and such are slightly corroded, and can benefit from a good cleaning. Ditto to all the connections to the dash from the main power supply of the ammeter gauge - corrosion means signal loss to heat, which is always a bad thing. Clean that shyte up!
Anyhow, hope this helps.