As we know all welders are different. But also depends on rod manufacturer.
Was welding cast with 1/8 Nickel rod last week and ran out. LWS is 30 mile away, so went to local auto parts store & grabed 1-lb. Nickel rod.
As per box recommendation there was 40 amp. Difference. Both 1/8 " and both 55% just different mfg. look on box just to be sure.