BTW, here is the contraption that I used to preheat the engine.
I plumbed the inlet to the 1500 watt coolant heater into the lower heater hose outlet from the water pump. The outlet went to the temp sender on top of the intake, while the other part of the T is connected to the disconnected heater hose. This way the block water was heated up. I tested it with the infra red gun and it read 180 degrees at the intake. The heater core and the radiator water didnt get the heat since the water pump was not circulating the coolant.
I had one of these same coolant heaters plumbed into my diesel Suburban and it would get the fluid real toasty in the winter.
The square thingy is a magnetic oil pan heater. You just stick it to the bottom of the pan and it heats the oil up to 100 degrees or so.
All together the parts cost about $60. Well worth the expense.