[Barnsnake]

When you shut your engine off, the heat soaks upward through the intake manifold and heats the carburetor. With the current "winter" gasoline this will cause a considerable amount of the fuel in the carburetor to vaporize and escape through the bowl vents. Since these cars don't have the vapor capture and recovery systems that production cars had after 1968 or so, you will smell it in a closed garage.
Once we transition to lower volativity summer gasoline, it will get better until the weather gets really hot.
A phenolic isolator will probably help, but it will probably not totally eliminate the odor.