Whilst staying with our friends in France in August, Alain was installing a two post hoist in his workshop. The photos below best describe how they did it, but I will just add a few points.
The original floor would not have supported a hoist being bolted too it as the slab was not thick enough, so the area had to be dug up anyway to put better concrete in.
The height of the workshop roof would not have allowed for a hoist with over the top cables etc.
The studs for the hoist to be bolted too we made from suitable diameter and strength rod with a thread cut ready for the nut later on. The stud then had lateral rods welded across them to provide additional bracing into the new concrete.
The end result of all this effort is that Alain's workshop now has a flat floor between the hoist posts - just right for pushing dead hydraulic Cits into place. The concrete had not set enough prior to us leaving so no demo pics were available.