05 reg cab, 4.7, long bed, 3.55. going from a 3.55 rear end to a 3.92 will this give me a greater tow load for my truck?

what needs to be done and replaced?

 

No greater load, but it will reduce strain while towing.
Is it a 2WD?
Replace the ring and pinion and the rear cover gasket.
4WD? replace both, front and rear ring and pinion and cover gaskets.

 

It actually does increase your tow capacity, because it lowers your final drive ratio. Tow capacity is rated on many factors, including rear end gear ratio, transmission gear ratio, engine HP and torque, tire size, weight of vehicle, brake power, etc.

However, after stating that, I wouldn't count on that extra tow capacity. Especially if you're new to towing or don't do it constantly.