That Al-U-minimum will transfer plenty-O-heat if bolted directly to a factory exh. manny, probably better than the OE iron with the extra transfer pins cast in.
Nope. Latent heat of vapourization of gasoline will easily and completely overcome whatever heat manages to conduct its way over from the hotbox. To get the job done, you need exhaust heat under the plenum, not in the middle between the two plenums. Offy did this right; Speco didn't.
You're probably right about this having started out as a twin-1bbl intake, though, now I look again at the carb mount pads.