A universal prop system for grid shoring provides increased versatility and cost effectiveness over conventional grid shoring systems for building construction, such as concrete parking garage construction. The universal props include a variety of interchangeable prop stands, interchangeable drop heads, and interchangeable stringer jacks with a variety of different types of stringer heads. The interchangeable drop heads interconnects the interchangeable stringer jacks with the interchangeable prop stands. The interchangeable drop heads are designed to support a variety of different types of rails, such as beams, joists, rafters, pipes, etc. The interchangeable stringer jacks include a number of different stringer heads configured to support a variety of different stringers. The different stringer heads include, for example, U-heads, spindle forks and jack plates, with and without detachable threaded shafts.