Any suggestions for new plugs for a 1993 6.0 XJR-S? Stock plug is a champion but Kirby's book recommends an NGK. Previous owner used NGK TR55 V-power R plugs.

Car will be used on the track beginning next spring.

 

I replaced the plugs in mine earlier this year, bought them from my local auto parts guy. He only had equivalents I think the brand was pulstar but when I went to fit them the electrode and ground strap was slightly longer than the originals even though the part number was listed as equivalent.

I ended up getting him to order NGK, which were exactly the same.