I used a shock mount stud in the trunk for the main battery ground. You also need to ground the block (starter)- I use the 3/8-in unused bolt hole that is in the middle of the block by the oil pan and attach it to the k-frame, it's virtually hidden. Attachment surfaces are critical, must be bare metal, free of paint, I also use special electrical grease to ensure no corrosion. Used #2AWG throughout, the cables do not even get warm with minutes of cranking & there is zero reduction in starting speed, works perfect. Note also the #2AWG fits nicely inside the right sill trim plate- just make absolutely sure it's fixed in position (I lightly attach it w/ non-hardening caulk) so you don't run a trim screw through it & burn your car down!