For you parts experts can you help me decipher the difference in these parts?

Parts and Accessories or Engineering #       Known Part #
         B6A 6049 F                           ECG 6049 H

         B6A 6049 N                           ECG 6090 H

I know 6090 is referenced to the engine cylinder heads.

Is the 6049 also a reference to the engine cylinder head?

All 56 and 57 parts.Thanks for any and all help.

Oldmics