Looks slick with the black stocks!
4" rear is kinda iffy when it comes to needing the adjustable arms. What really matters is if the driveshaft still has enough slack in it when the suspension is bottomed out to not bind and be shoved up into the trans tailhousing. I think what usually drives people to get the arms is to push the axle back to center it in the wheel well because it moves forward the lower you go.
If it were me, I'd lower the jack with the rear coils out and shocks disconnected until the axle is bottomed out on the frame, then see if the driveshaft has any longitudinal play. The other reason for the adjustable arms is to set the pinion angle with such a drop. I think the stock geometry is pretty good at keeping the pinion angle within tolerances, but it doesn't hurt to be sure. Magnetic angle gauges are cheap and plenty useful elsewhere, so they're a good investment.