Hi,
If you decide to go to an electric fan and do away with the old fan, you might want to consider removing the fan extension and replacing it with a harmonic balancer. This is a must on a TR4, I'm not sure how critical it is with TR6.
Yes, Geo, that's a neat, simple mounting method! Wish I'd thought of it before I mounted the 14" fan on my TR4 (Mr. Gasket brand).
My main motivation installing an electric fan was just to not have to worry about it. The original 4-blade metal fan and long-neck radiator had done the job without fail for years, even at high altitude on 100 degree days, with Webers, increased compression, headers and a few other performance modifications.
Still, I had visions of a blade flying off and skewering the radiator! After all, the same 4-blade fans put 2 out of 3 TRs out of LeMans the first time Triumph entered. They pitted and removed the fan from the third, to prevent a three-pete. A fan wasn't really needed at an average speed of 114 mph anyway! (Salt in the wounds of the two cars retired by it.) But the third car DNFed for some other mechanical reasons anyway.
A 12" or even a 10" fan is probably adequate for most TRs, and is what the TR vendors sell. But on my car it's also pulling air through the oil cooler, so I opted for slightly larger (1700 cfm is overkill for a 2.4 liter engine). 14" hangs over the sides slightly, but shouldn't present any problem.
One of the trickiest things was finding a fan assembly that was thin enough to fit behind the radiator on a TR4. I've got less than half an inch to spare. Better measure on your car to see how much room you have, and watch that dimension on any fans you consider.
In my opinion, a puller fan and a thermoswitch to control it are the only way to go. The kit I bought is a reversible fan, can be changed to use as a pusher or puller, and came with good wiring, connectors, a relay and a self-resetting circuit breaker in case of overload (no fuse to worry about). The thermoswitch was a separate item (on at 180 F, off at 170 F) and came with a weld-in bung to fit it. It's now installed in the lower hose pipe of the car.
Another thing to watch out for when adding an electric fan is whether or not your alternator (or generator) is adequate. Bigger, high volume fans can draw upwards of 10 or 12 amps, by themselves. My car's generator was only good for about 17 or 18 amps, but I was changing to an alternator and thin belt system/harmonic balancer anyway.
Summit Racing has a huge selection of fans and competitive prices. The Delco #7127 alternator I picked up at a local parts store (rated at 60 amps, but tested at 76... time to beef up the wiring!). The thin belt conversion/harmonic balancer came from British Frame and Engine, not sure if one is offered (or necessary) for a TR6.
Cheers!
Alan