Many differences most notably the DCOM uses a diaphragm type accelerator pump and it has a vacuum port for vacuum
advance distributors. Some the innerds are interchangable with a dcoe but not many...I would really stick with a dcoe if I were you, avoid headaches of trying to track down parts. Supposedly they are 'better' but I havent seen any proof either way. Actaully I havent heard much of anything about these carbs....If you're looking for more flow maybe consider a dco, bah who needs a choke Good luck to you.
A few sales on ebay, decent picks....look very similar to a dcoe, havent been able to dig up a diagram of the innerds, I'd be interested in seeing it if someone knows a link.