[Dimi]

Hi Geof
I run a Boss 260 in my GT40 and on the heads there is a hot water outlet pipe that comes from each head and goes to the thermostat housing.

I silver soldered a short length of copper tube to the side of one of these pipes and slid the sensing tube into that.

It picks up the heat coming out of the motor and can be adjusted via the adjusting pot to switch on at whatever temp you require.

The advantage is it still works extremely well and doesn't compromise the integrity of the cooling system and is easily removeable for servicing/replacement.

It can also be fitted to the radiator in the same manner near the hot water inlet to the radiator if this is more convenient.

Dimi