Which is best rear axle?

A 3.73 axle will give you the best gas mileage while a 4.10 will do a much better job with getting that heavy trailer moving quickly but will also cost you in mileage as they cause the motor to run at higer rpms when cruising down the highway. 4.10s are normally found in 1 ton pickups and above with dual rear wheels that are designed to handle heavy loads and trailer weights.

I would recommend a 3.73 ratio for all applications except where you are going to be towing really large and heavy loads on a daily basis.

do not buy a 4.10 gearing....it is way powerful and kills the gas mileage by atlest 6-7 mpg and with the powerful v8 that the chevys allready come with you wont be needing it

3.73, change differential oil every 30,000 miles. Or before you pull something heavy for a long distance. I'd use Mobil 1 gear lube.