Outer Limits 4x4 Board

I have an OME suspension system on my vehicle but have added coil packers to the mix and am considering rotating the rear axle to improve the driveline angles, allow the coil springs to sit straight and centre the wheel in the wheelwell I should be able to run a longer travel shock but how do I calculate the length I will need?

Run your truck up a ramp and measure then add an inch-and-a-half. Next order ya shockies