Andy - just a thought, avoid buying a HR if you don't have one now as some of your components will not fit a HR engine...seems to be a lot more expensive tuning up the HR at the moment too.
If it was me, honestly, I would move on from the Z now. May bring back bad memories - just try and take the positives with you going forward and look to another motor. I'm sure whatever your build thread would consist of and whatever car it may be, we will all be following with great anticipation.
Change the motor, but not the forum.