WHICH "Vortec short-block"? 305? 350? Have the heads been milled? Block decked? Unusual-thickness head gaskets?
I'd expect the rockers will have to be self-aligning. The pushrods "should" be OEM length for roller cams.
Biggest problem I see is folks who can't find the true "zero lash" point when trying to adjust the lifter preload. Either they're trying to "spin" the pushrods as they tighten the rocker nuts, expecting the pushrod to stop spinning at "zero lash" (it won't, it'll continue to spin until the lifter has collapsed) or they're adjusting the valves in the wrong order so the lifter isn't on the base circle of the cam lobe.