I'm running stock nonadjustable rockers and pushrods, but my XE268 is in a 400 BB. No issues since it was put together in 2003. I have run stock rockers in a 440 with a Comp 292 magnum for 25 years with only one outright rocker failure. They can wear and get sloppy on the shaft after awhile though. Lifter preload may not be correct with the stock nonadjustable setup. You won't know until you put it together. Sometimes the tolerances just won't stack up in your favor. The few small blocks I've owned had stock cams so I have no personal experience with the reliability of the stock SB rockers when using a hotter cam.