For years I used manually controlled electric fans - effective but I always wondered if they blocked significant air when off & driving at speed.
As a side note, I use only an electric fan, mounted as a puller. I finally built an automatic controller that works, but ran for many years with only a manual switch, first 15+ years on my previous TR3A and then on the current TR3. I tried keeping the stock fan with the TR3, but it got hot coming home from TRfest 2009 (big traffic jam on the 101, almost 2 hours to go 30 miles) and I decided to go back to the electric setup from the 3A.
Although powering it can be an issue (I'm still running the original 19 amp generator, you should have the later, larger unit) I really like the result otherwise. The fan never comes on at speed, only when I stop suddenly (eg freeway offramp) or I've been sitting at a light for more than a minute or so. Running a 185F thermostat (no sleeve and bypass fully open), and the gauge never goes above the '5' in '185' (which is where I have the fan set to come on).
115F is about my limit as far as ambient temperature goes, but the engine stayed cool. And I really like no longer having to keep one eye on the gauge all the time.
It's my belief that the electric fan poses significantly less restriction mounted as puller instead of pusher; possibly even less than the engine mounted fan does. As a puller, the fan freewheels at higher speeds, allowing the air to pass with relatively little restriction.
But my experiment with the Stag seemed to show that mounting the electric fan in front of the radiator reduced air flow at speed. Might not apply to all cars, and YMMV, but it ran hotter at speed with the electric pusher than with either the stock crank-mounted fan or no fan at all. (I went back to stock as soon as I could find the necessary replacements for the broken parts.)