I am trying to figure out which hose you guys have your water temp gauge installed in?

I would think to get the most accurate, hottest readings, you would want the hose running FROM the engine to the heater core and not vice versa but, I don't know which one that is based on water flow direction.

There is a hose running from the very front of the intake to the firewall and one coming out of the firewall right beside that one that goes to the back of the engine/intake (can't really tell), so which one is it?

 

HI!... You want to install your temp probe into the heater hose that goes from the intake manifold to the heater core nipple facing the driver's side of the firewall. That location is the ingoing coolant line.