Jeff you have a few things assembled wrongly. Check you have the diff mount the correct way around. From memory they will go on either way but only one is correct. The moustache bar appears to be facing the wrong way and is on the wrong side of the hangers.
As for having to drill the holes out in the moustache bar I suspect you either have a different model bar or the diff end plate is not an original one. The moustache bar should have tension on it as it acts as a spring to keep the diff in the forward position.
Attached is an assembly diagram that may be of assistance.
Maybe so. But I've also seen several 240Zs with substitute diffs installed and their non-matching moustache bars mounted whichever way round to best fit and installed incorrectly. People use whatever they can get their hands on to get mobile. So take measurements off an original car if you can.