[LMH]

Just a note in case you don't already know, rebar is sized in 8ths. #4 bar is 4/8" or 1/2". #6 is 6/8" or 3/4" and so on.
Depends on what the wall is made of course but 8" of concrete is not thick enough to support a block wall. Local code here would need 16" of depth (I think that's current local code) for a block wall plus two #4 bars. Here, it would also need rebar/concrete vertically in the block voids every four feet and a bond beam above the window lentals. It gets pretty crazy in Tucson for codes sometimes!
Larry