Note: Flashing a radio by any method can brick your phone if something goes wrong... which it shouldn't. Flash at your own risk. It worked for me, for what that is worth.
HBOOT Flashable Radio Download.
Download the file, rename it to HERCIMG.zip.
Place HERCIMG.zip on the root (top level) of your SDcard.
Reboot into bootloader, or hold VOLUME DOWN + POWER from power off.
Make sure you are in HBOOT mode, if not read the screen on how to get there.
Once HBOOT is up, it will automatically find HERCIMG.zip and scan it.
You will see it found a radio and wants you to press "ACTION" to continue.
Press the trackball once, then wait. Once it's finished you can reboot.
You are done.
Thanks to Nfinitefx45 for posting the radio in his ROM thread, post #2.
S-OFF Method I used can be found here.