I know on the actual b15's, to access that bolt the crossmember needs pulled down with the rear motor mount still attached to see the hole the bolt goes through bracket mount attaches. The mount actually sits in the way. Now I have pulled tons on b13/b14 trans and I never remove the crossmember at all. And I don't know how a b15 trans looks in a b14 but I just recently pulled some and had to drop crossmember on both b15's in rear to get to the bolt inside the hole.
If that helps.