Lifting the battery negative seems pointless, as there are numerous spots where various devices have their own negative wire to the body and chassis.
I would lift both wires from the battery, give it about 15mins, check there's no residual voltage and clamp the negative & positive leads together. This should prevent any induced voltages across electronics.
At the welding site, I would put an earth clamp either side of where I'm welding. This should guarantee that no stray currents nick off across bearings, etc.
If you're really fussy, make sure the vehicle is insulated from a hoist or jacks so no electrical paths can be caused back to the grid earth.
From what I've read over the years, it seems that some people would hook up the earth clamp somewhere on a vehicle and start their welding. Later, wheel bearings would fail (micro arcing) and possible electrical faults appear. Unwittingly, they caused return paths through these things.
Don't let the b'strds get you down!!