FWIW, you can make use of the awkward bolt-hole at the back to simplify the job slightly. Test-fit the rock-slider to ensure it's all going to work. Put an 8mm rivnut into that rear hole immediately, raise the slider back up again, screw a bolt into the rivnut hand-tight, lift the front into place with a jack, make sure everything's aligned properly (check the doors can open and the shut-lines are acceptable), put a wooden dowel in one of the front holes to ensure the slider can't move, tighten the bolt into the rivnut... and then you can climb underneath and drill all the required pilot-holes with the slider in place. After that, you can loosen the bolt slightly, allow the slider to hang down at the front, finish drilling all your holes and then lift the front back up again.
Ideally, yes but the chassis rails are roughly 12" inboard which creates a couple of problems. Firstly, because the chassis rails are so far away from the sills, there'd need to be some seriously heavy-duty steelwork attaching the rock-sliders to the chassis or the brackets would allow the rock-sliders to bend upward when there was any weight on them. Secondly, and possibly more importantly, if you built rock-sliders that were strong enough to attach to the chassis rigidly, forces applied to the rock-sliders could cause the chassis to twist. Bolting the rock-sliders to the sills isn't a perfect solution so you'd probably pick a different vehicle to use as a dedicated rock-crawler but, for more general off-roading, these work fine for those times where you might, for example, drop a wheel off a step or drive over a rock big enough that you would otherwise damage the sills.
FWIW, you can make use of the awkward bolt-hole at the back to simplify the job slightly.
Test-fit the rock-slider to ensure it's all going to work.
Put an 8mm rivnut into that rear hole immediately, raise the slider back up again, screw a bolt into the rivnut hand-tight, lift the front into place with a jack, make sure everything's aligned properly (check the doors can open and the shut-lines are acceptable), put a wooden dowel in one of the front holes to ensure the slider can't move, tighten the bolt into the rivnut... and then you can climb underneath and drill all the required pilot-holes with the slider in place.
After that, you can loosen the bolt slightly, allow the slider to hang down at the front, finish drilling all your holes and then lift the front back up again.
Shouldn’t these be bolted to the chassis and not the body?
Ideally, yes but the chassis rails are roughly 12" inboard which creates a couple of problems.
Firstly, because the chassis rails are so far away from the sills, there'd need to be some seriously heavy-duty steelwork attaching the rock-sliders to the chassis or the brackets would allow the rock-sliders to bend upward when there was any weight on them.
Secondly, and possibly more importantly, if you built rock-sliders that were strong enough to attach to the chassis rigidly, forces applied to the rock-sliders could cause the chassis to twist.
Bolting the rock-sliders to the sills isn't a perfect solution so you'd probably pick a different vehicle to use as a dedicated rock-crawler but, for more general off-roading, these work fine for those times where you might, for example, drop a wheel off a step or drive over a rock big enough that you would otherwise damage the sills.
🤘 *promosm*