best way to measure spring pad width?

not sure if this belongs here or in drivetrain tech, but I'm swapping my 7.25 for a Dana 44 rear end, and the car it came out of was tubbed and the leafs were moved in-board. I need to weld new pads on it because I'm keeping the factory location springs and I need to know how Id find the correct placement to weld the new pads on. any suggestions?