I filled at the radiator in the rear, hooked up a normal scavenger system recovery tank (open). Opened the front vents at the heater lines and filled at the radiator. Air is going to migrate to the highest spot, filling from the rear, moved most of the air to the front and vented out of the heater line T´s and the radiator filler cap..
Was carefull to make the filler on the radiator and the highest point of the cooling system in the motor, pretty close to level (radiator filler was slightly higher, maybe 2 inches).
Maybe there was a small air trap in the system or the system some way or the other, just produced it´s own air, don´t really know. Had to peroidically, bleed a little excess air out of the system, at the motor. Overheated a bit, a couple of times, until I figured out what was going on.
Just have to figure out someway to let the air out when you fill and to periodically release whatever air moved to the motor side of the system. Just somehting you have to keep an eye on and check periodically.
Some type of T and vent at the highest point on the top hose, near the thermo housing, might help to vent some air missed by the heater hose venting methode.
May be a better way of venting the air, that I just haven´t thought of yet. What I had worked well enough.
If you can find or build a thermostat housing with a hose outlet and a stand pipe with a sealed (non vent) cap and made the radiator cap very near the same highth. Filling and getting the air out would be fairly easy.
Rear radiator, cooled really well, used like a 12" fan most of the time (slightly build 350 Chev. in a one ton truck), as a puller (rear to front) and had a large 2 speed 16" pusher on the other side of the radiator, I used rarley.
Most of the air behind the cab, moves from the rear to the front, might be different on another model truck. But the best air flow on mine was from rear to front, with the radiator, near vertical and a closed bottom bed.