2004 Discovery 4.6l 124k.
Actively dripping coolant from passenger side front, wet front drive shaft.
Leaks/drips while running only
White smoke on start up
From above the engine bay I can see coolant leaking at approximately the height of the exhaust manifold but the leak is on the firewall side of the motor so I cannot see the source as well as I can see the trickling stream.

Looks like a duck, quacks like a head gasket.

phone of the vantage point where I can see flowing green coolant at back of motor/firewall.

 

If you look at the pictures of block or head surfaces you can see the small coolant passage at the corner - if you truly have white smoke in the exhaust that is the likely culprit. You will probably lose the O2 sensor on that side also (assuming you have antifreeze in it). It's conceivable its the intake manifold at the rear, running down the back, but those are less common. You could check the plug on cyl #7 to see if it is steam cleaned.

With power tools - 4 to 6 hours apart, 8-12 hours back. Chase the head bolt holes with a tap before going back. Clean the oil passages in the rocker base towers if they are plugged up - make sure every thing goes back in the same positions.

Good luck