Chris,
Picking the right gear ratio involves many variables. Choosing a rear axle also requires making some desisions as to bolt pattern and size of bolt pattern. I am not 100% positive about the burb bolt pattern, but I believe it is larger than the standard GM passenger car pattern. Unless you are going to swap the front axle with the later model parts, (Bolt in) you might consider using a passenger car axle. If you want to keep the 6 lug in the front you can get a K10 rear axle that should fit your truck, with the appropriate gear ratio.
There are many gear calculators on the web. You can do a search at
www.hotrodders.com and find a list of some of them. Here is one I found by doing a Google search.
www.rocky-road.com/calculator.html It is geared "no pun intended" to 4x4 use, but has many different calculators that will help you determine which wheel, tire, and gear ratio combination will work best for you. One last thing, as if there could ever be a last thing when working on old Chevy's, you need to consider the wheels you will be using on you truck. Will you be using stock, off the shelf custom or custom made wheels? Making these desisions now will help you choose which axle will work for you. One more last thing, see I told you there is never a last thing, if you have a stock rear axle in you C10, it is probably a higher ratio than the 4:11 ratio.
Chris, welcome to the BB, I hope my comments have helped and not confused you. Do some searches here, there are many posting on this subject.
Well, I just can't resist the temptation to give just one "last" bit of information. As LONGBOX55 said, you might want to use the 4:11 rear axle and change the transmission to an overdrive trans. A T-5 five speed would be a real nice choice.
