in aaroncakes grounding procedure article calls for m6x1.0 & m8x1.75 stainless bolts would anyone know the length

 

your only "height adder" is the thickness of the copper ground tab, which can't be more than a few mm at most. The one on the engine block though, the M8 bolt, it *might* also go through the rats-nest piece of steel, can't recall. If it does I'd add an extra 5mm to the length of the bolt to compensate

I'd go for 15 mm length everything to start out w/

 

It's noncritical. Seriously, just use any bolt. 0.75" would do the job.

Since you asked here I won't reply to your PM asking the same question.