I've done this twice, a 156 one time and a 159 on my '98. I used the polaris heavy springs on both of them and they were expensive. I don't know about aftermarket springs but have no doubt something is available. The 159 I did a drop n roll so I moved everything around and it's not really relevant, but the '97 156" is a stock skid and still has excessive sag even with the heavy springs. I never went any further with it because it's just a spare, it looks kinda goofy but it works fine. The only way to really compensate is to move the location of the rear scissor mounts, either on the skid rail or the tunnel mounting bracket. If you move the bottom of the scissors they need to go back or if the top it needs to move forward, you need to slightly extend the scissor movement. Maybe look at an '01 151" 800 compared to the '00 136" 800 and take some measurements, they are basically the same skids as the '98 extra-10. Good luck