I am getting this 67 FJ40 frame ready for proper V8 mounts, new shock towers, and a Saginaw box setup but all the PO weldments had to come off first. What I found to work the best without digging into the OEM frame steel is documented in the pics below.
Using a 4" x 0.045 cutoff disc and angle grinder I scored the welds on the sides, almost down to the frame steel stopping just short as not to dig into it. On the top weld I scored it all the way across, again stopping short of the frame steel.
Once the scores were done I used a small chisel and 5lb hammer on a top corner to start the fracture and then moved to the middle of the top face.
Using a 4" x 0.045 cutoff disc and angle grinder I scored the welds on the sides, almost down to the frame steel stopping just short as not to dig into it. On the top weld I scored it all the way across, again stopping short of the frame steel.
Once the scores were done I used a small chisel and 5lb hammer on a top corner to start the fracture and then moved to the middle of the top face.