One should never provide an additional ground conductor path... One ground wire/cable from the ignition module to the engine ONLY.... Typically plug cables provide the connection between the engine block and spark module.

Typically the ground braid is attached to the base of the sparkplug (sometimes with a hose clamp). The other end is attached to the aluminum case (internally). This is the (only) correct configuration.

No extra ground leads should be attached from the (aluminum) ignition box to the engine.

One can ground at the sparkplug base (best), or from the aluminum casing to the engine block. You can have one, or the other, but not both.

The best is the shortest distance to GND, which would be the braid attached to the metallic plug base or right nearby. A shorter length of braid is resonant at higher frequencies. Making the braid as short as possible has merit (just enough slack to act as a strain relief against engine pulses) and crimp a HD eyelet on. I then drill the nearest cylinder fin (close to the main cylinder head mass) and bolt it on using Loctite. (This eliminates the hose clamp provided with some ignitions and associated problems)

Never solder the eyelets to the braid, as this has just defeated the strain relief right where it is needed most (right at the junction where the braid enters the crimp area).