Gungadin,
Having lived out here on the coast but also back east where it does get a little brisk in the winter, I can say, we don't even know what "cold" is out here. On v8 cars, I used to block the exhaust heat crossover even back in Michigan. A bit fussy in winter but it helped in the summer. (That should answer your 2nd question - YES, you can have "too much" heat, and the result is less power - it is only 1% or 2% but why give it up for free when we pay hundreds of dollars to get each small gain?)
The classic factory examples I can think of here that I've lived with are [a] the Ford Pinto and [b] the Triumph Spitfire. Both were inlines, neither had exhaust heat to the intake. The Pinto had water heat only and did just fine all across the nation. The Spitfire had no heat at all and again did just fine.
I do find out here that we can experience ICING - but that is due to lack of carburetor heat, not manifold heat. On the 283, Chev ran exhaust heat to the base of the carb just to guard against that. A closed snorkel air cleaner with a home-made heat stove will stop icing, you might build one for the Langdon's if needed, and just run it in the winter if it's ugly.
I wouldn't hesitate at all to run those Langdon's unheated out where we live. And they are doing quite well in Tom Lowe's "Dyno day for a 250" as you can read!
