I'm not sure what the difference is between the converters, but the model number for the latest model 4L80E is 25A-20L, instead of this one, which is 25-20L. I asked Hughes if they could convert this one to work with the newer trannies (since that's what I have now) and they said no.

So the answer to your question is that you can't make it work with your 03 trans.