This is pretty good info and shows a good depiction of the frontal structure:
"The Anatomy of An Elk: Proper knowledge of shot angles and placement is “vital” - Western Hunter"
https://westernhunter.net/tactics/t...wledge-of-shot-angles-and-placement-is-vital/
I think this is more accurate on spinal structure from a broadside view.
View attachment 197036
There was a discussion about heart vs. double lung a while ago. I'm not sure how you get heart without hitting the lungs on a broadside shot.
As far as how far forward. The leading edge of lung is typically covered by the front leg and shoulder bones. Ahead of that is neck on a straight broadside shot (same for deer) unless his leg is significantly back while in motion. You need a quartered to or frontal shot to find the leading edge of lung. You can find lots of debate on that.