I've done this twice recently on two vanagons. Seems the best way is to
put a 13 mm box wrench over the top, then go below with at least a 12
inch extension and a 13 socket. Be sure to watch what the wrench hits
when you turn it or you might mash a brake line.

Getting them back in wasn't too bad, I packed newspaper under the bolt
heads (you'll see what I mean when you look) to make the thread ends
stand high enough to put a nut on them. Once the nuts are started on
the top, remove the newspaper packing. Then apply the box wrench above
as in removal, go below with an extension, and tighten.

Jim