Re-number main parts

I have 12 beams that should have been the same. Inadvertently 2 (205A) of them had different copes than the other 10 (200A). I did not notice this until I numbered and detailed the beams. I have since made all 12 beams the same but would like to get the 2 numbered the same as the 10 so I have 12 (200A) of the same beam. I know how to delete the small and main part numbers of the 2 (205A), but how then do I get them numbered correctly and update the quantity for the total 12 (200A)? I have tried to just re-number the 2, but the small and main part numbers come up with new numbers. Does the system not recognize that the 2 beams are now identical to the 10 and name them accordingly? Thanks

To tell if there are differences between the two beams/assemblies see attached picture.  Once it says "No differences found" don't select the two beams, if you have other stuff in your model you don't want renumbered select the 2 beams plus the other 10 then renumber and if they are the same it will make the numbers the same.  Once you've numbered, and they are the same numbers, update your details in the drawing manager 

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