Whatever you think of the death penalty, allowing an executed prisoner to redeem himself by organ donation completely undermines the rationale for executions by turning murderers into heroes.
I have to ask why it matters from whom these organs were harvested? From what I understand the receiving party never knows where the organs come from. Information about whose organs they were and where they are from, although presumably not impossible to piece together, is not available. If the process is supposed to be anonymous, then who is left to praise the donor? Certainly donor cannot revel in this fact (unless you believe in moral properties existing beyond the limits of a person's lifetime).
Stronger, pragmatic arguments against the process are far and away more convincing. The practical difficulties alone are why Americans should consider avoiding the practice. Statements like this one should have been leading the argument:
Execution makes it hard to obtain organs. Some forms of killing—electrocution, poisoning—ruin organs.