The best 10mm plug I have found is the NGK CR8HIX and Denso IUF-24
1/2 inch reach, resistor, fine wire iriduim extended electrode, and taper cut ground.
The NGK has a 0.6mm electrode and the Denso has a 0.4mm electrode.
I was running these in G230s and G260s in boats and turning 14,000 with 25:1 oil mix.
Very resistant to fouling with the high oil content, very good noise suppression, and work well with mag ignition even with the wide gap. (By the way, do not attempt to regap these. You will break the electrode. They come factory set 0.32)