Great job there
McGyver, I'm thinking of doing similar with my 75 Club SE. KV6. 2.5 petrol auto. As the coil-wired feed from down in the wheel well (Pas/side)has disintegrated. The addition of the larger pipe reducer will in fact assist airflow, since the reduction increases flow speed. ( Ram effect.) Not certain of how this can be adapted to suit the Rover 75 but, I will add pics once the mods been effected. Well done you for both sourcing and achieving a grand looking modification.
*nb: All Rover75 KV6 owners. This leaves a very large vacant area in the said wheelwell. The opposite well contains the washer bottle which holds as much liquid as does the cooling system in total. Large eh?
Here, (o/s) I'm considering fitting an additional radiator, (increased volume and cooling area) or alternatively a second expansion tank, again to add more coolant. Nothing ventured as they say ......
For all those implying the KV6 has NO overheating problems I dispute this since mine has given nothing but problems over the 12 months since purchase. (*In again now for a final rad change.) Thus far ...
Fitted a Hans temp guage ... new Kenlowe Fan and control box ... all hoses now have jubilee type clips large or small ... new metal Stat housing and thermostat ... removal of fan cowling for improved airflow ... finally a new rad. After this either `she' behaves or it's "up the Ebay road" I've had enough.!!! I'm beginning to think it's a case of "over engineering" what was otherwise a very good car. End of rant.
Mike.