Alice You transposed the Century and the Decade of Winfield Scott's birth. It was 1786, not 1876. You are correct he was 75 in 1861.

I am not sure that Lee would have been chosen as Scott replacement upon Scott's retirement had there not been a Civil War. There were many more men ahead of Lee in seniority in 1860 who were already full Colonels and Generals before the resignations started to take place in December of 1860 and into early monts of 1861.