I agree with what Fred & BALLS wrote 100%. I bought my entire setup, 1-stop shopping, from Dan @ Clear Image Automotive.
The 3.73s was the first mod I did to my 9C1 a few months after I bought her. It was one of the best performance upgrades I made, second to a PCM tune, which you will need once the work is finished.
I have over 100,000 miles on my rear, and contrary to to the myth that some people write about, I have been using Amsoil synthetic gear oil for the entire time. The Marine who installed the rear for me, told me to do that, and I have had ZERO problems.
You'll want to seek out someone who does rear end or transmission work for the upgrade. Don't just go to the local guy around the corner. You'll want to research this a bit. A recommendation is to seek out guys that do a lot of 4X4 work, as they usually upgrade/change gear ratios a lot.
Also, as far as axles are concerned, what Fred wrote is also right on the ball. I didn't need to R&R the axles when I upgraded the rear end. Typically the only thing that will ever go wrong with an axle is the outer surface where it rides on the axle bearing.
If you do need axles, go with Moser. I did upgrade my axles about 4 years ago and went with them, and it was a perfect fit with killer quality.
Clear Image Tri-Ys & Hi-Flow cats >> 2.5" X-Pipe & Magnaflow Tri-Chambers, Mike Harris 4L60E, Circle-D 2,400 RPM TC, All MOOG FT End & Del-A-Lum bushed MOOG CTRL Arms, Eibach FT & New Stock HT rear springs. Hotchkis Sway Bars & End Links, RAISS, 3.73 Gears in Eaton carrier, Dynoshaft & CIA Loop, BMR Trailing Arms, Braided Brake Hoses, Taylor Spiro-Pro Wires, AutoMeter Water Temp & Oil PSI Gauges, Impala Console. ATE Blue Brake Fluid. Skip White distributor. 20's, Z28 Cluster, Corbeau GTS Seat