Mark 20H clamp bracket casting #

[Heliarc]

Is the correct casting number on the original Mercury Mark 20H clamp bracket 1400-21? Thank you.

[JohnsonM50]

Ive got one here that on the port side has a Merc insignia over #s ND 3651 F ALCOA C - [the Cs inside of a square diagnally set so it points up & down] then 28. It has a 20 H type tower with the enlarged steering brake area?? These are raised #s Mike