OK, thanks ST24 for the info, ended up I couldn't get the subframe bolt out anyway. McGainer, I read that thread, and to me it sounded like dropping the subframe would be easier, but didn't know what the alignment involved, so went ahead and did some wrnech-grinding.
I ended up getting the right one off with the modified wrench, but the left one was too tight against the body. We loosened the subframe bolt but it got stuck about 3/4" out, even the impact wrench wouldn't turn it anymore. We pried the frame down but still didn't have enough clearance, so my brother somehow managed to force the new bushing into the bracket while one bracket bolt was still attached.
The sucky part was, after spending most of the weekend doing it, I still have the clunky sound that made me go in there and do the bushings to begin with.....