I'm looking for anyone that could provide a "Ballpark" guess of cost to change rear axle gear in my truck to make it more suitable for towing.

Info:
07 Silverado 1500 W/T 4x2
5.3L Engine, 4-Speed Auto
3.23:1 Rear Axle
43,800 mi

Looking to change to 3.73:1 or possibly 4.10:1

I'm in the Raleigh NC area so anyone with local experience is a plus.

Thanks in advance for replies.