I am going to take time to post how I ran heater supply lines through the cowl on a build I am doing. Nice and tidy, and takes those big ugly hoses off of the firewall and the engine. This may not be everybody's cup of tea. Flame away.
Starting with the windshield wiper cowl (or whatever you call this area) open, it was time to run the tubing. The hole is an access to the rear bolts on the suupercharger cover. It has a cover made from an old AC unit panel. For the heater supply lines, I used soft copper so I could shape it to the curve of the cowl. My step bit wasn't long enough, so I welded a drill bit on the end to make it longer.
Soft lines formed into place.
I use these fittings by Watts, because a 5/8 or 3/4 heater hose slips right over, and secures without slipping.
Pressure testing the system to 20 psi
Tank and soapy water
Cap one end, pressurize the other.
Done. Man those are ugly hose clamps. Maybe I should replace them.