4.10 is base.
https://www.gm.com/content/dam/compa...olet-Truck.pdf
If an optional ratio was chosen it would appear on the SPID, calling out the specific ratio by RPO and noun name (ie, "GU6 3.42 axle" or "GT4 3.73 axle").
The base ratio typically is not shown (because it varies based on model, series and powertrain) or may be shown as RPO "GQ8 Base Ratio".
K
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'63 LeMans Convertible
'63 Grand Prix
'65 GTO - original, unrestored, Dad was original owner, 5000 mile Royal Pontiac factory racer
'74 Chevelle - original owner, 9.85 @ 136 mph best
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