Another small block turbo early valiant

Prine said
Well, I found the NGK GR5s to be the root cause of it.......

I swapped the entire turbo setup onto a 318 and installed NGK 5671-9 plugs gapped at .028" in it and had no further issues, even up as high as 14psi on pump gas.

Not doubting you, please tell me about the setup that died and how you determined the plugs were the root cause.