2bbl to offy dual port questions....

I don't know the 550's model number of hand but I know it was running on top of a 360 with a torker 2 so I know it will run.

My 2 bbl is in the motor now and could use a rebuild so I figure now is the time to change it over to 4bbl (damn ethanol)

The offy has a dual plane already and the spacer I have also has the divider.

What would the pros and cons be if I used the spacer?