Similar to Post #21, I made a saw horse a couple inches taller than the rear body sill, jacked the rear of the body up with a floor jack & 4x4, slid the saw horse under, lowered the floor jack, took a single chain with hooks to each front body mount holes, centered that chain on a come-a-long hooked to a chain on the truss above (reinforced across adjacent trusses and angled 2x's from the floor), raised the front of the body enough to roll the chassis out, then lowered to another saw horse or dolly. Note: though the weight on the truss or tie is half of the body weight, check that truss or tie and adjacent ones, and reinforcement pieces for knots, cracks, etc.