Hi Erin-
I'm no expert on this, but I put a 3.42 from a late 90s S-10 4x4 in my Chevy 3600 and couldn't be happier. Other than needing new spring perches and slight drive shaft modification it pretty much bolted in. There is a slight difference in axle width- I have some offset on the rear wheels.
Now that "Ernest" can go 60+ MPH, I also put a 1/2 ton front axle with a new disc brake kit......... and some seat belts.
Hope this helps- Also, try the "Search" feature- there is lots of info on here about this.
