Hi Ralph,
Although I had and eliminated an electric fan a while back, I installed a switch under the dash that interrupted the ground and connected the positive to a fused shared hot line coming from my alternator. I did have a temperature sensor that cut the ground once the radiator temperature fell below that specified so could run after the car was turned off.
When mounting my fan, I attached the unit to the cross braces as many other recommended. However, as found by others, this positioning blocks the flow of air when under way and resulted running hotter then without the fan. I also have a TR7 that I eliminated the air conditioning and resurrected the use of the cabin vents. I later eliminated the engine fan and now depend upon the 2 small retained, radiator-sensor activated, auxiliary air conditioner electric fans mounted low and at an angle to the radiator. My experience with this set-up is quite good and the car runs at normal operating temperatures on the hottest day in traffic and the fan do not block radiator air flow when underway.
Although I guess it would be difficult to mount a single larger fan low and at an angle to the radiator out of the driving air stream, I thought I would extend the idea as it works quite good.
One last point; the TR7 has a sealed radiator bulkhead so hot air recirculation when the car is stopped is not an issue as I believe it is on the Healey with its porous radiator bulkhead and drawing fan. However, a forward mounted electric fan could help mitigate this issue of hot air recirculation if the electric fan's air stream pushes forward-escaping hot air back or to the side and diminishes it recirculation through the radiator.
Just some thoughts,
Ray (64BJ8P1)