Why do Wagon frames have the inspection holes on the front frame spring pockets, I would assume this was some sort of provision to shim springs possibly? Perhaps big block cars had this frame as well. I've had two 61 Wagons and both had these 2" diameter holes on the backside of the spring pockets, never had them on my Convertible or two other Bubbletops, but those were all small block cars.
Were they all from the same frame manufacturer?
No, St. Louis and Los Angeles, both original documented cars.