Ring/Pinion Gear change - HELP!

Hi - I own a 2003 Dodge Ram Van 1500, 5.9L, 3.55 R&P gears. I am attempting to have the gears changed to 3.92 or 4.10 to achieve some extra towing power, however, no one seems to know what will be affected by the change - now even the local Dodge dealers know anything. I have talked to an expert in gear changes and was told that most likely the speedo will need to be recalibrated, but no one knows anything about what else is affected such as fuel injection, transmission shift, etc. Does anyone know exactly what needs to be done to change the gears?

Thank you.

A gear changhe in the rear end will not affect any Engine controls like Fuel injection. As far as Transmission shifts will not be adversly affected, however you will notice a lower Mph at the same rpm of a shift, and you will notice more off line torque, Top speed may be reduced a few Mph, use this to figure your exact numbers. Divide the 2 ratios 3.55 divided by 3.92 or 4.10 = < should be less than 10 %)to get a percentage, then drive at towing speed (rpm) to get MPH, then you can use the percentage to get new MPh at the same RPM, (Example: I went from a 2.41 gear to a 3.73 gear on another vehicle which produces 20% change.) if you need exact numbers i can have them in a few days, i too have the 3.55 gear and was thinking of 4.10 for racing.