It sounds like you've had way too much taken off the block halves.

Stock gaskets are 0.7mm I've had blocks skimmed in the past and still been able to use those too. I'm running 1.1mm gaskets now without issue.

Do you know the history of the block i.e has it been decked before?

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605whp
Quarter Mile in 10.9 seconds @ 135mph /217kph
0-100 kph 3.2 seconds