Do you have the rochester one barrel? If so, yes, you can take the top off while it is mounted in the truck. And, if you're careful, the horn to bowl gasket will remain intact. However, as easy as these carbs are to remove, I find it easier to pull the carb and disassemble it on the workbench, especially if you have to clean varnish out of the bowl, which usually involves soaking in carb cleaner overnight.
