Bob,
First off, I assume it is a factory GT5S, and not an owner-modified version?
If so, then......
I HIGHLY doubt it is the original factory block.
Just can't imagine a 1972 engine sitting in the Modena factory for 15 years only to be installed in a GT5S.
I ... think ... the GT5S cars all came with Aussie-sourced Clevelands, so the Aussie heads MAY be factory original.
That makes some sense if the stock block was destroyed but the heads were retained.
Larry
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