Here is a calculator so you can run "what if" combinations.
http://www.summitracing.com/expertad...tio-calculator
The change from 4.10 to a 3.73 is about a 10% change. If you are trying to turn a truck into a freeway flyer an O/D would be a better choice. A Gear/Vendors would be my first choice behind a TH400. Maybe switching to a built 200R4 or 700R4 automatic would be easier for you. There are also bolt in Spicer/Dana 60 rears with 3.54 gears found in big block trucks. That would be about a 15% drop in RPM across the board, kind of like being in O/D all time.
Without knowing how you plan to use it, it is hard to make strong specific recommendations.