Back when the 940 was made 30 ish years ago, NGk and most other spark plug manufacturers used to say to always use anti-sieze compound. Spark plug technology may have moved on (including the V-groove electrodes) but the head is still the same as it was in the 70s, 80s and 90s - as such i would go with the major part (the head) and still use anti-sieze compound. Then fit the plugs using the time-honoured nip it up finger tight then 1/2-3/4 turn with the plug spanner.
If the supply of Bougicord leads has been exhausted in the UK, i'd go for Denso instead :
https://www.rockauto.com/en/catalog/...plug+wire,7224
Cleaning and re-applying heatsink compound to the ignition amp was part of the next stage in my process. If you decide to do it now, when you clean it do NOT use anything abrasive, just use solvent cleaners and finally a fine metal polish like Solvol-Autosol to get the heatsink and back of the ignition amp to a smooth, shiny surface, cleaning off any residue of polish afterwards before applying heatsink compound. Also worth checking the earth for the ignition amp, easily found by following the loom from the plug to the nearest earth point, usually about 6-8" aft of the plug as a bad earth there will reduce the output. This will be most noticeable under the most difficult firing conditions, i.e. under cruise conditions as a weak mixture is the hardest to fire.