The problem is the ebay info isn't verified, it's the sellers ad. If you want proper tech advice about those particular springs, contact Comp Cams about them rather than ebay. Odd thing is from what I see, they should work with the X cam. And yes, performance valve springs will be taller than the wimpy stock springs. They'll be 1.750 inch tall when installed, and you won't get coil bind until 1.150 inch.