No matter if it is a TT head or an NA head and he used TT plugs or NA plugs the piston, is not going to hit either of the plugs. That is what I am trying to say. If he used TT pistons and TT rods then the compression ratio is going to be a stock 8.5. Even if he uses the TT head or the NA head. The Question is can he use a TT plug In an NA head and and NA block with TT internals. And the answere is yes>>>>>>>>