Forward just in front of the mast. Aft in line with the companionway so that the sling is forward of the saildrive, although some yards like to place the sling aft of the saildrive if it is a travel hoist. If you are having it lifted by a competent boatyard they will know where to place the slings.
You can find a profile drawing of the underwater shape in the B34 plans list which can be found in the owners manual section of this site - last post on the first page, or on the sailboatdata site.