You need a full tank.

To do it by the book you would need weights but if using a Hunter Hawkeye machine you can align it without the weights.

If your camber is excessive now, and you can't get it within spec in the rear, you have worn lower swing arm ball joints and/or wishbones and you would need to replace those before realigning.

I also strongly recommend rear toe set to -.01 so you save your tires, even if camber is within spec you want that toe closer to 0 to save your inside of the tires, the toe in the rear is what shreds them on the inside, not the negative camber.

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2018 Ram 2500 6.7L Cummins 68RFE
19k miles -Bright White/Black - Big Horn Sport - Crew Cab Short Bed
2013 X5 35D (CEO's) - Born on 5/17/2013 -
82k miles - Alpine White/Cinnamon Brown/Premium Pkg, Sport Activity/Premium Pkg and Sound/20" Style 214/Running Boards