Hi I got a decompression plate from mad-for-it as well and all I can say is it was so wrong it was unreal.
It dose look good against the head gasget but when you put it in to Pos on the block Its all wrong. And the Pistion hole size is to big. The plate is to small width ways as well.
Its the same plate they sell for the ZVH convertion.
Check it out if i was you.

That is unless they have changed it since then.

Ferd