Perkins 4-107 Calorifier connections

[SteveY]

Hi
Would anyone know the plumbing arrangement from and to a Perkins 4-107 for a calorifier?
A Perkins 4-108 in the boat yard has out coming from port a) and return to b), but as you can see from the attached photo port b) has the water temp sender connected.
Would the return go to any of the other available ports in the exhaust manifold c), d) and e) or should it return to heat exchanger f) or somewhere else?
Thanks