[IndyIan]

The water temp was measured using the stock water temp sensor in the block and a scangauge. This was after the car was started but was the first number that popped up on the scangauage. I think water temp from that sensor would be ambient before starting the car even with the block heater but I've never looked to see what it was.
We have a timer set for about 1-1.5 hours before we hit the road.

I don't think the coolant and especially the rad is that critical to pre heat.
There isn't much(maybe zero) flow through the rad until thermostat opens up, the water is going through the engine and heater core if open.
I watch my air intake temp(my car has a WAI) and it shows the engine bay doesn't get heated up much at all until the water temp gets near 80C opening the thermostat, then it goes up about 30-40C depending on how fast I'm going.

Also since the thermostat won't open until the 80C or so, a 1/4 mile drive will put the coolant in the rad back to ambient until the thermostat opens.

I just happen to have block heaters already and they seem to work fine, its seems a katz heater will work fine too if installed properly. I just don't know if its that much better than a block heater.
Ian