I'm in the process of refinishing my inflatable and want it install lift rings to use for davits on my sailboat. Can anyone tell me where to place these rings on a dingy that has an air floor and do I use a three or four point system

depends on the 3 point lifting harness you have and the way you plan on lifting (davit or by your main halyard)
drill 2 holes in your transon and install 2 -1" eye bolts. then glue a 2" "d" ring to the inside bow section tube about 4 inches from the top of the tube. be sure to use a ring using backing material that is the same material as your boat (pvc, hypalon)

should help!