EDIT: That link was definitely part of what I was researching at the time (as it is linked in the project article I posted and I remember reading about the limitations regarding stereo output, as well as the line "Most radio receivers want a signal to be an odd multiple of 0.1 MHz to work properly").
https://makezine.com/projects/raspberry-pirate-radio/
Using this disk image for the RPi:
http://cdn.makezine.com/make/pifm/PiRadio.zip
(good times)
EDIT: That link was definitely part of what I was researching at the time (as it is linked in the project article I posted and I remember reading about the limitations regarding stereo output, as well as the line "Most radio receivers want a signal to be an odd multiple of 0.1 MHz to work properly").