All of my motors have run better (and leaner) with a heated intake manifold. Especially those with multiple carbs. It's not a cold weather deal at all, rather better atomization of the mixture. Others have had similar results, but for some reason the 250/292 motors seem to be not so critical. I have no idea why this is so.
Correct on the GMC thermostat housing. Here's a picture of one on my motor:
[img]
http://www.inliners.org/images/Halton_GMC_01.jpg[/img]
One of my 261's has the same housing, they are interchangeable. Langdon's Stovebolt probably has a few used ones kicking around.
