Zach Hamilton of Hamilton diesel has been working on new valve springs for the 6.0 for a while. He finally got them in a month or so ago. Specs look pretty good.
Here is how they compare to a stock spring
stock 6.0 Hamilton 6.0
1.840" 70 100
1.800" 82 111
1.750" 98 126
1.700" 115 135
1.650" 131 152
1.600" 148 166
1.550" 165 181
1.325" coil bind 247
1.250" coil bind
Here is how they compare to a stock spring
stock 6.0 Hamilton 6.0
1.840" 70 100
1.800" 82 111
1.750" 98 126
1.700" 115 135
1.650" 131 152
1.600" 148 166
1.550" 165 181
1.325" coil bind 247
1.250" coil bind