I don't see how it can cause engine damage
The hot exhaust gas erodes the metal of both the cylinder head and the exhaust manifold, creating a progressively bigger leak. Eventually the pulsation of the pressure in the exhaust system starts pulling cold air through the gap and can warp the exhaust valves from the constant temperature fluctuations. There's also a distinct fire hazard in case of the inevitable gasoline leak that running a Rochester carburetor presents. All it takes is one spark or backfire from a leaky exhaust gasket to burn the truck down.
Other than that, no problem!
Jerry
