For the #5 tube......on the A body Hemi builds, for additional clearance, I cheat the steering shaft as far left (drivers side) as possible, often slotting the firewall bracket slightly to get all I can get. A small amount at the firewall yields quite a bit at the shaft end.
You can see now why the Hemi sits where it does.....your mod for the Stage V heads is probably the best way to go.....not much room to move the motor more to the left.
It is a dance to find the perfect location.
Lastly....I would ADVISE to not dent anything until you get the actual block in there. I have read of too many issues from relying on the plastic blocks for critical clearances.