intake manifold doesn't seem to fit well

[hawaiigrady]

Boat is a 1992 Grady White Explorer. Engine was apparently replaced in 1997. Intake manifold was leaking (all around) so we pulled it and found that doesn't line up well with bolt holes.

New (1997 installed) engine casting number is 10243880. I assume this is Vortec engine

Heads have casting number 14102193

Manifold has 12 bolts. Casting number GM 1409(8)242 (I think it is an 8). Also a Chevy emblem. And 16DN, and number 18436572

Carb is Holly 4 barrel

Can anyone tell me if I have the wrong manifold or heads for this engine? And what the correct configuration would be?

Thanks! WOuld love to get this boat running and fishing...

Aloha,
HawaiiGrady