The carbs are not too much and you don;t need to lower the cfm.
Where ever you got that idea its false. The carbs are fine.
They will need jetting adjustment. Start with stock default jetting but plan on dialing them in.
The tunnel ram needs some specific set up to be responsive on the street.
But the size of the 600 eddy carbs is not a problem.
Get that out of your head.