They will bolt up, but the tube location to the bolt holes are offset enough that they will not line up properly, and the flange will cover about a quarter of the port, and have a pretty gnarly exhaust leak. Plus, I'd imagine the flanges may get in the way of the spark plugs, depending on how they are cut. So... short version is... you can, but shouldn't.
This also goes for gaskets... upside down gaskets really can be a lame situation... not that I have ever done that before...
