[rotorwrench]

Canadian 69A engines from that era also had separate replaceable bearing shells but the 69A casting mark on the block should be evident. None of the USA made blocks had anything but floaters in that time frame unless modified. Other sources of knock could be piston related if something made it's way into a cylinder or if the clearance was reduced too much by excessive planing of a cylinder head. Also check your exhaust for blown manifold gasket. One more thing would be a broken ring or burned piston. That can make a audible noise at low rpms. Compression would be low on the offending cylinder in that case. Piston slap is notable on very worn pistons.

In general, the early Ford V8 engines didn't have very high oil pressure. The indicating system after the war was basically a 60 PSI system. It's not uncommon for well worn engines to drop pressure to minimums after they are warmed up on a hot day. Driving is slow paced urban environments or pulling heavy loads didn't help since the flatheads could easily overheat if coolant flow was impeded by crud in the radiator or due to a bad thermostat if so equipped. The floater bearings did manage to be able to take some pretty low pressure.