Look for a differential or a set of gears?

[BigRandy]

My project is a running 74 C-10 Cheyenne, 454 with a TH400 and 3.73 gears. I'm guessing it 60 is a comfortable speed for the motor as it sounds like it's turning around 3 grand at that speed. The 3.73's are quick but the truck runs out of fun once I hit 3rd gear so I'm thinking about getting rid of them.

I've never done any work on a differential and would like some opinions.

Should I try my hand at installing some 3.42's, 3.08's, or find a complete unit from a junk yard and go with that? What's a fair price for a salvage yard rearend?

Thanks!