Best spark plug for dual fuel (LPG / petrol)?

[Ilya]

Quick question, running a Legacy 2004 MK4 H6 EZ30 engine, with an LPG conversion on Dual fuel with petrol.
Spark plugs need to be changed but which of the NGK should I go for?

The original ILFR6B or the LPG7 with the lower heat level? Would the LPG7 cause issue when running on petrol?

And a question as for the torque, the NGK recommend 25-30Nm while I believe the manual said 21Nm (I’ve lost the manual and using the one online)

Thanks.