Jack; I'm really hesitant to suggest this as you can damage things by doing this, so take extreme caution.
You can put a breaker bar w/socket onto the bolt and wedge it against the frame. Very quickly, and only just a very quick snap, hit the starter (ignition key). This will almost always break the bolt loose. BUT....it the breaker bar comes loose, or you crank the starter too long, you CAN damage things. So, if you try this, be very careful. I've seen breaker bars end up in the radiator, which is not a good thing. Can ruin your whole day. NOTE: THIS IS NOT A RECOMMENDED
SUGGESTION. SEVERE DAMAGE COULD RESULT. (disclaimer)