Which spark plug? -2011 VE series 2 omega sedan dual fuel alloytec multiport 3.6 V6

Which spark plugs goes with this car? and do I need NEW INTAKE MANIFOLD GASKET to replace plugs.

My confusion is there are petrol plugs and then there are LPG plugs..which one goes with factory duel fuel car that runs almost in LPG mode.

Then there are iridium, double/single platinum...

Just want plugs that last longest and are suitable for duel fuel.

Thanks