Can you confirm the model number? I'm aware of a TKR-720 (repeater) and a TKB-720 (basestation), but not a TK-720 (which following Kenwood conventions should be a VHF mobile radio).
You should be able to read out the Frequency EEPROM with an EEPROM programmer. You'll need to check what EEPROM your radio has fitted -- my TKR-820 had a Rohm 93SC46, which will program as an ST 93SC46 (the latter seems to be more widely supported).
In the case of the TKR-820 - this uses some kind of Hirose connector I haven't been able to identify. I soldered on a Molex KK connector with a bit of wire, then made a jumper which went from that to an 8pin DIP with the EEPROM's pinout.
Here's the pinout for the TKR-820:
TKR-820 front panel EEPROM connector:
8 6 4 2
7 5 3 1
1: DO (EEPROM pin 4) - red
2: DI (EEPROM pin 3) - yellow
3: CLK (EEPROM pin 2) - green
4: EN1 (EEPROM pin 1) - blue
5: EN2 - not connected
6: RST - connect to GND to hold unit in reset (programming mode). Float for normal operation.
7: GND (EEPROM pin 5) - black
8: no-connect
If the EEPROM is socketed, just unplug the thing and plug it into the EEPROM programmer
You can probably use the KPG-21D programming software to create an EEPROM image. I'd read what you have out and keep it as a backup first so you can put the radio back as it was.
The file created by the KPG-21D programming software contains the Frequency data in the first half, and the Signalling data in the second half. I have no idea if the TK-720 supports CTCSS...
If the EEPROM format isn't the same, this might help you a little:
http://www.repeater-builder.com/kenwood/tkr-n20-bit-banging/tkr-n20-bit-banging.htmlCheers,
Phil.