A bleeder hole isn't really required for our old stuff. But if air pockets concern you the best way to fill the cooling system is the vacuum method. No air in the system at all if you do that, which is also the way the factory did it and the reason older cars had a spring in the lower hose.

I got a fairly cheap kit on Amazon, pumped my cooling system down to 23.5" and filled it with new coolant. Done. No air pockets, no burping the system.

https://board.moparts.org/ubbthread...1951-plymouth-cambridge.html#Post3043150