[aluminum]

IT's NOT DEAD IT's Damaged :
Heat and water in the bearings is your major Enemy.
If you Got the Motor Hot Hot Hot could have Collapsed a piston
If enough Water went through the Bearings / Crankshaft then you Have damage .
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Most Likely you have some damage and will see low Oil Pressure after replacing the head gaskets when the Motor is completely warmed up > Piston May Knock .
Only real way to tell is to disassemble the motor and mic everything.
I would say with a lot of experience the missing is spark Plug Misfire due to water in cylinders.
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As It's a High performance Engine With a Aluminum Block Head Gasket damage Means More then just the Gasket often . Galvanic Corrosion can be a issue ( That's Why you need a Aluminum friendly Anti Freeze in such Motors ) Block Wear, Deck Height , The Cylinder Coating .
On and On >> 928 like Distilled Water Mixed with The Right Anti Freeze related to such issues .
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Another Way is to Pull the top Down * Bad side first * Inspect the Block Head gasket Area Very Close * Straight Edge the Block for wear Also the Cylinder . If all Looks Good throw a Set ( not one) of Head gaskets on it and all other top End related gaskets > Some Not so costly Oil and Filter and Run it a Hour to Bake out the rest of the Water ( under 3 K Revs ) Then change the Oil again and Filter . and see how it works >> Should be able to do all that for a few Hundred .
Not really Gambling if The block & Cylinder Looks Good it is good but have someone who know what they are looking at look with you .