If I plug my fm stero into sound card line in what is the best quality audio I can record at ( ie bitrate mhz ect...)
Depends on how demanding you are!
Try to record in the highest quality as possible. However 192kbit/s - 44,1 mhz should be enough. Just try and look what think is enough!
If I understood you right, you want to record from your radio FM-Tuner with you soundcard?
Well, the quality of FM Stereo is often compared with the sampling quality 32 kHz, 16-Bit, Stereo.
But I don’t think, that you can compare a transmission technique with a sampling technique this way.
I would recommend 44,1 kHz, 16-Bit, Stereo for recording.
The source material on radio stations is also often recorded @ this rate (CD, MP3, an so on).
Maybe you wanna filter the 19 kHz multiplex pilote tone before recording …