Mike,
You put much torque to that rear end and you are going to rock it back and snap your U-Joint. Those springs aren't going to resist much drivetrain wind-up. I broke a U-Joint with no lowering blocks with that same number of leafs. I wound up putting a trailing arm in to keep the axle rotation under control under hard shifts.
I don't see any running boards . . . no bed . . . does the truck have a cab on it? What size tires you planning on running? I think you might be surprised when you get the weight back on the truck how much those springs are going to sink. I have driven an AD truck with barely enough ground clearance to snake a jack in under the running board . . . I didn't use any lowering blocks, only removed a few springs and used 14" rims with low profile tires.
