the under dash floor board illumination bulb is courtesy lamp bulb and it is in most all the late 70s and 1980s big cars and trucks and etc... it is a single filament low amps draw, around 3 amps or so,, as stated already.
was a very common bulb for a ton of different vehicles and applications/locations,,
even also alotttt of cab roof marker lamps as well..
but this size bulb had a billion different part numbers, all depending on what brand,,,,, but 1003 is a basic general 15 candlewatt power bulb for these single filament bulb sockets such as under dash and etc in the 1970s 1980s etc. and is what is listed by GM directly, as the bulb originally factory installed for these. but there are many many more other bubls of different CWPP levels that fit and work as well, in these bulb sockets.. including 1056 and many other 10XX series bulbs
