So much changes ,your
better off just buying one as opposed to trying to make yours work.
Here are the reasons why:
Converter height {measured with hub down on the bench to the bolt pads}:
4l80 = 6.870 - 6.920
2004-r = 5.855 - 5.905
The cover will need to change or the pilot and bolt holes lengthened
Pump hub diam:
4l80 = 1.998 - 2.0
200-4r = 1.746 - 1.749
Hub in the pump side of the converter will need to change
Turbine hub will need to be changed as well.
4l80 = 35 spline
2004-r = 27 spline
The rest of the converter is typical 9.5'' stuff.
Mike.