Unfortunately, the bottom plate only houses the throttle blades and is called the throttle body assembly or more commonly the base plate. It does not do any sealing of fuel in the carb. It's really not that hard to seal the plugs on the bottom of the main body (float bowl assembly) while you have it apart. Taking the base plate off the bottom of the carb is easier than taking the top off. And there are differences in air horn assemblies (top), so if you still want to swap parts around, you should bring your other carb with you to make sure they are the same. Does your top have four tubes sticking out or six? (Did they put them back in correctly after machining it flat?? - maybe this is where your bogging problem is). Check to make sure both have secondary fuel discharge ports just above the secondary air valve as well.