Ring / Pinion Gear Change - H:ELP!

I have a questioin for anyone that may be able to help. I own a 2003 Dodge Ram Van, 5.9L, 3.55 R/P Gears. I am attempting to change the gears to 3.92 or 4.1o, however, no one seems to know what else will be affected by the gear change such as the Speedo., fuel injection, transmission shifting, etc. Does anyone out there have any information on what procedure needs to be followed when changing the R&P gears on this type of vehicle (not even the dealers around here know).

Thanks.

Transmission shift points and Lock/Up will be effected for sure, and fuel economy will go down. I will have to do some research but on Chevrolets you can replace the Drac and fix this but I can't remember right now if your ecm can be reprogramed for this gear change I will get back to you on this.