My mercruiser 454 (GEN V) has an aluminium intake manifold # 6269318.
(“rectangular port aluminium” is all info I can find on the internet.)
= “quadrajet” spread bore

I bought a (as good as new) EDELBROCK 4BBL carb # 1407 2199
= square bore / 4 same sizes plates

Which adapter plate do I need? Any part numbers?

The edelbrock carb should have both bolt patterns, so an adapter is not needed.

Carb is too low to manifold, so spacer plate is needed ...

As long as the throttle plates on the carb will fully open when installed on manifold.

Gotcha, Edelbrock 2696 is the part you need then.

Perfect, thank you fast replys
regards peter