Zippy...is your shortblock assembled already? I hope you mocked up the valvetrain and checked pushrod clearance on the block and heads before you started putting it together.
I had a LOT of time in checking clearance and grinding for the pushrods on my KB block. Dan Costello also mentioned it would likely be an issue w/ the World block also. I haven't built the World block hemi I have here yet so can't comment for sure.