Difference Between 862 and 706 Heads

[tsmurphy72]

I am trying to figure out what the difference is between these two cylinder heads which are used on the 5.3L. The info I find states they have the same runner size and combustion chamber size. The only thing that appear to be different are the years they were used but this is vague. Does anyone know the difference. Will they both work on 2001 5.3L
Thanks.