A conventional transceiver can be keyed for QRSS work using ON7YD's QRS software. I often do this using my TS-480 to run 5 Watts on the 80m and 160m.
The software is versatile, easy to use and provides a keying output on both serial and parallel ports. Here is the circuit diagram between the port and the transceiver keying jack:
Note that it requires no source of power. I use an old serial port cable with a small Manhatten style pcb at the transmitter end for the components with the output leads clipped across my hand key.
The help file included with the software explains everything and ZL2IK has more info at his blog
ON7YD developed his program back in the dark ages of QRSS when it was virtually impossible to find a keyer that would send at our low speeds. It was actually the keyer used when I built my first QRSS rig 10 years ago. I've used it off and on for homebrew rigs as well as recently to key my TS-440 and TS-480. It's definitely a handy accessory to have around the QRSS shack.