Depending on your planned amperage, and even just to be safe, I recommend using a pillar. I know the d-ring holes are used, but the path from the sheet metal in front of those holes to the chassis is questionable in my view. Grounding directly to a pillar means you're going right into thick steel with solid weld points leading to the rest of the chassis. Here's a look at my 2/0 ground on the driver's side c-pillar. There's also a smaller spare 8AWG ground that terminates here (just a backup; it's un-used now). Everything flows through the 2/0 now as it should.
The little oem hole on the left top is where I previously had a very small ground. It's no longer used and is now painted over.
Some points: buy a jar of no-ox-id from amazon, and after sanding away all paint from the pillar steel, apply a very thin coat of it to all exposed metal.
For the bolt, you can just use stainless since most of the current is passing through the direct contact between the lug and the pillar steel. At the time I did this I used copper bronze hardware, which Schneider Electric likes, but I later swapped it for stainless. The bolt really shouldn't and doesn't need to carry any current in a proper ground.
Star lock washers are recommended for electrical, but I used a nord-lock and a nyloc on the backside. Typically you wouldn't use nylocs with electrical, but with a beefy 2/0 cable and the relatively reasonable current levels I expect to push (at 48V), there's very little chance the nyloc will ever reach 200F (melting point). Even if it does, the nord-lock is still there, and it's the better fastener anyways.
The wires are wrapped in Tesa heat tape, which was mostly to offer abrasion resistance.