I do believe that 300 feet lateral clearance was the FAR 121 standard for the OEI case at one time,
ah, my knowledge base increases in the usual exponential fashion .. as you are aware my background is not in 121. Thanks for the heads up.
From an engineering and operations viewpoint, I take the position that 300ft lateral is somewhere between unachievable and incomprehensible without LLZ-accuracy electronic track guidance ....