The Cobra S/C or Comp 427 FE Engine - What is the real thing?

[CobraAddict]

In my continued journey to enlightenment in trying to build myself an authentic look/feel Cobra 427 S/C, I have now gotten to the engine.
There are many high qualify engine builders in the states and I am hoping to engage with one of these to build me a period correct 427 FE side oiler with medium rise heads , single 4 barrel Holley etc, etc.

Now I was under the impression that the Comp and S/C cars had the 427 with the alloy heads, magnesium intake manifold and alloy water pump.
However a particular well know engine builder I am liaising with is adamant that this is not the case, at least not for the two examples I told him I was interested in emulating, the S/C CSX3045 or the Comp car CSX3016. He claims both of these cars have the same C5AE-F cast iron medium rise heads and Sidewinder aluminium intakes and not the aluminium heads and magnesium intakes that are suggested in the literature I have. He claims that in 1965 the only aluminium heads available were for the experimental GT40 program!

So my question now is what makes up a period correct Cobra 427 FE side oiler engine for an S/C and a Comp car? Does anyone have any accurate specifications they could share?

Aside from the twin carbs and detuning, what other differences were there between the Comp and S/C engines?

Another unrelated question I have. I assume the radiator expansion tank should be black yet I have a reference photo of an S/C, CSX3021, where they make reference to the ‘proper Ford Corporate Blue’ radiator expansion tank! Yet it’s the only one I have seen that is blue!?
What colour should it be?

Best Regs from Oz