TA says the Rover heads are based on their V6 aluminum heads. TA recommends the NGK R5671A plugs. They are racing type plugs with a recessed nose. Since the reach is 3/4" with those plugs, I don't see why you can't use the same plugs that fit the other aluminum heads, like the BP_ES plugs or the FR-5 that I use. They are more suited to street driven cars. https://www.ngk.com/search/all?q=R5671A https://www.ngk.com/ngk-7373-fr5-v-power-spark-plug
