Buy the gasket set with confidence. For the job intended, the gasket set is a perfect match.
The differences between a P40 and a P engine gasket set, are for the timing gear cover gaskets, and the water pump that are totally different, and easily done. In my case, I've used the P40 gasket set a couple of times. For the timing gear cover, I've used silicone and no gasket. Not a problem.
The head and manifold gaskets are exactly the same.