You need preload adjustment to set your sag, but there's a limit. You can’t increase or decrease your preload indefinitely, if you’re almost at the maximum setting either way you’ll need other springs. That said the S10 only has rear preload as far as I know so the front is what it is. If you want to set sag in the front you’ll need other springs to get into the range you want. By my reconning you’ll need to be at about ~20mm static sag and ~60mm rider sag. Also pay attention to the compression and rebound settings, Dave Moss has excellent videos on YouTube about it. I mention it because if set wrong it will eat you tires, they’ll scallop like crazy.