if you have the transmission crossmember unbolted, lower the transmission a little bit. it'll pull the engine down with it and give you clearance in the trans. tunnel to stick a long extension with a swivel and a 13mm onto both of the top bellhousing bolts.
if the jack supporting the transmission is already all the way down, then try raising the car a little bit.
if the jack supporting the transmission is already all the way down, then try raising the car a little bit.