Maybe we've taken this to the other side.

The question you have to ask yourself, Is the Converted Device Usable for street Navigation or Not ?

Logic Tells Me.

Device is usable for accurate street navigation > Keep it as 3490
Device is not usable for accurate street navigation > Revert to 3790

The Fact that it might show +- 10 meters Accuracy VS 4 Meters Accuracy might just be incidental to the different GPS Chipsets.