[Mercury694]

It's got a thermostat, so I don't see any reason to worry about any significant problems. I'd think the main issue is making sure you keep the warm water on the engine side of the thermostat while trying to get as much of the block running warmed water as possible. If you take water from the water pump (lower radiator hose) you should be running it through the return line from the heater core to get the most exposure for the block. If you're looking to make sure your feet are warm first thing, you could route it through the heater core circuit as a whole, with the understanding that you are sacrificing some of the heat. I don't see any technical issue, the question is whether or not the water heater can keep up with the load. I suspect it will be fine unless it was marginal to begin with. Make sure your temp slider is always all the way over on "Hot" when the block heater is plugged in so you don't deadhead the block heater.