papa;
I think you've got more than one issue here. The reason you couldn't shut it off is because that "batt" terminal on the HEI should go to the "run" terminal of the ignition switch so that when you turn the key off the HEI doesn't get power anymore.

As to why it ran "full blast" - make sure the throttle plate in your carb is completely shut when your foot is off the petal. The idle screw or a stuck linkage could hold it open. Did you put starter fluid or raw gas into the carb, that might have done it too.

I doubt that running for 8 seconds would hurt the engine too bad although it certainly didn't do it any good. That open hole in the valve cover probably needs to connect to the carb through a pcv valve. Make sure any vacuum ports on the carb and manifold are either connected to something or plugged.

That's all I can think of at the moment. Hopefully others will chime in.