Update: I decided to upgrade the carburetor on this engine and installed Fenton cast iron headers and a Clifford intake manifold with a Holley 390cfm 4 barrel. The manifold is heated with engine coolant, which I routed with hoses through and through the manifold on the path taken by the bypass tube described above. This is not as efficient at heating the carb as the stock paired manifolds or an electric heat plate, and the truck is a little cold-blooded, but once it warms up, it delivers pretty muscular torque. The rig is a '54 GMC 2-ton and will haul a load of gravel no sweat. Passes everything but a gas station . . .
