The SM7B is famously great for many applications, but it may surprise you to hear that it works quite well for rock acoustic rhythm guitar. It gives the guitar a very focused, concise sound. Not so much for delicate ambient finger style instrumentals, but killer in a rock mix. Read more
Set it flat and aim it at the neck/body joint, pointed a bit away from the sound hole and about 6-8" out. The mic has low output, though. I usually use a Cloudlifter with mine.