An assembly comprising: a gas turbine engine comprising: a gas generator portion; a power turbine section arranged fluidly downstream from the gas generator portion, the power turbine mechanically disconnected from the gas generator portion; a power turbine rotor locking assembly comprising: a rotor shaft; an aft rotor stage surrounding the rotor shaft; a locknut torqued to the rotor shaft; and a plurality of torque resistance features (78, 86) located on an aft side of the aft rotor stage; and a tooling fixture having a plurality of corresponding torque resistance features, the corresponding torque resistance features selectively engageable with the torque resistance features of the aft rotor stage to resist circumferential movement during assembly and disassembly of the locknut with the rotor shaft, the aft rotor stage defining a circumferential cutout on an aft side of the aft rotor stage, the circumferential cutout at least partially defined by a flange; characterized by the plurality of torque resistance features on the aft side of the aft rotor stage are a plurality of radial tabs extending inwardly from the flange; and the plurality of corresponding torque resistance features of the tooling fixture are a plurality of slots selectively engageable with the radial tabs of the aft rotor stage to resist circumferential movement during assembly and disassembly of the locknut with the rotor shaft. a gas turbine engine comprising: a gas generator portion; a power turbine section arranged fluidly downstream from the gas generator portion, the power turbine mechanically disconnected from the gas generator portion; a gas generator portion; a power turbine section arranged fluidly downstream from the gas generator portion, the power turbine mechanically disconnected from the gas generator portion; a power turbine rotor locking assembly comprising: a rotor shaft; an aft rotor stage surrounding the rotor shaft; a locknut torqued to the rotor shaft; and a plurality of torque resistance features (78, 86) located on an aft side of the aft rotor stage; and a rotor shaft; an aft rotor stage surrounding the rotor shaft; a locknut torqued to the rotor shaft; and a plurality of torque resistance features (78, 86) located on an aft side of the aft rotor stage; and a tooling fixture having a plurality of corresponding torque resistance features, the corresponding torque resistance features selectively engageable with the torque resistance features of the aft rotor stage to resist circumferential movement during assembly and disassembly of the locknut with the rotor shaft, the aft rotor stage defining a circumferential cutout on an aft side of the aft rotor stage, the circumferential cutout at least partially defined by a flange; characterized by the plurality of torque resistance features on the aft side of the aft rotor stage are a plurality of radial tabs extending inwardly from the flange; and the plurality of corresponding torque resistance features of the tooling fixture are a plurality of slots selectively engageable with the radial tabs of the aft rotor stage to resist circumferential movement during assembly and disassembly of the locknut with the rotor shaft.