I would have real concerns about any item that plugs into the 1.8K on the 75. This is because of the small bore coolant runs on the engine and the real dangers posed by any drop in coolant available to the engine (HGF).
I know it doesn't help but I suspect that there may not be enough total coolant to run both the heater and engine - in that case if the heater is taking essential coolant away from the engine then that would be trouble -i.e. over heated and thus warped head etc.
If it was my engine then I wouldn't do this fit
hth and good luck
