Awesome! It's a much nicer sounding OPAMP huh? Modifying heatsinks to go on them is tough. One might be able to easily make a version on their own, anything really, that's metal and connected.
Replacing signal capacitors will give you a good improvement. But by far the best thing I've done is an LDR for the input resistor. I know people are like "OMG the distortion!" well how about the "OMG IT SOUNDS ALIVE!" factor that's much more noticeable?