Followup-For: Bug #871269 Hi Dirk,
for libgslcblas0 the Replaces on libgsl23 needs to be versioned (<< 2.4+dfsg-4). All the Conflicts can probably be turned into Breaks (which will make apt's life easier for distupgrades involving this transition) and Breaks and Replaces need to match w.r.t. to the versioning (otherwise you might run into weird corner cases). Andreas