A rotor stack for a gas turbine engine, comprising: a first rotor disk with a first rotor spacer arm, the first rotor spacer arm having a first flange with an outboard flange surface and an inboard flange surface, a first hole along an axis through the first flange, and the first hole comprises a first counterbore in the outboard flange surface; a second rotor disk with a multiple of integrally mounted blades and with a web having a second hole along the axis; a third rotor disk with a third rotor spacer arm, the third rotor spacer arm having a third flange with an outboard flange surface and an inboard flange surface, a third hole along the axis through the third flange, and a third counterbore in the third hole in the inboard flange surface; a bushing with a tubular body and a flange that extends therefrom, the tubular body comprising at least one axial groove along an outer diameter thereof, the bushing extending through the first hole, the second hole, and partially into the third counterbore in the inboard flange surface of the third flange; a fastener that extends through the bushing along the axis; a nut threaded to the fastener to sandwich the web between the first flange and the third flange; a cold-side groove from an outboard plenum along the inboard flange surface of the first flange to the first counterbore; a hot-side groove along the inboard flange surface of the third flange to the third counterbore; and an output groove along the inboard flange surface of the third flange from the third counterbore to an inner plenum, wherein the rotor stack is configured to permit a desired mixture of airflow from the outboard plenum forward of the blades, via the cold-side groove and along the outer surface of the bushing, and airflow from a plenum aft of the blades, via the hot-side groove to the outer surface of the bushing, into the inner plenum, from the outer surface of the bushing via the output groove. a first rotor disk with a first rotor spacer arm, the first rotor spacer arm having a first flange with an outboard flange surface and an inboard flange surface, a first hole along an axis through the first flange, and the first hole comprises a first counterbore in the outboard flange surface; a second rotor disk with a multiple of integrally mounted blades and with a web having a second hole along the axis; a third rotor disk with a third rotor spacer arm, the third rotor spacer arm having a third flange with an outboard flange surface and an inboard flange surface, a third hole along the axis through the third flange, and a third counterbore in the third hole in the inboard flange surface; a bushing with a tubular body and a flange that extends therefrom, the tubular body comprising at least one axial groove along an outer diameter thereof, the bushing extending through the first hole, the second hole, and partially into the third counterbore in the inboard flange surface of the third flange; a fastener that extends through the bushing along the axis; a nut threaded to the fastener to sandwich the web between the first flange and the third flange; a cold-side groove from an outboard plenum along the inboard flange surface of the first flange to the first counterbore; a hot-side groove along the inboard flange surface of the third flange to the third counterbore; and an output groove along the inboard flange surface of the third flange from the third counterbore to an inner plenum, wherein the rotor stack is configured to permit a desired mixture of airflow from the outboard plenum forward of the blades, via the cold-side groove and along the outer surface of the bushing, and airflow from a plenum aft of the blades, via the hot-side groove to the outer surface of the bushing, into the inner plenum, from the outer surface of the bushing via the output groove.