Problem fitting new left manifold on 512 BBi

We have a problem installing the new exhaust manifold (left side) on a 1983 512 BBi (chassis 46435) in spite of two attempts (this part was sent back to the supplier after the first attempt and came back to us again).
I wanted to know if a similar situation already occurred in the past on this model.
All other new components (right side manifold and exhaust) from the same supplier are fitting as expected.
The supplier has offered us to return all the parts and to reimburse the purchase, which we found surprising.
The supplier received the very original left manifold as a model.
The problem is that the new left manifold cannot go around the chassis and be connected to the exhaust without bending and forcing the parts significantly (see the attached pictures), which of course we do not want to do as we feel this would put the engine block at risk.
Thanks in advance for any advice.
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