We use the Microchip ICE2000 emulator with the appropriate module.
These are available on eBay for a reasonable price. I don't recall the module number but can get it tomorrow when I'm at work.
FWIW - we use the 12F675 instead of the 12C671 / 12C672 for all new designs. Less expensive and contains eeprom as well as a better a/d converter.
Why do you want to use the 12C672 when better parts are now available? These new parts are pin compatible with the older parts.