Can I replace my 1990 K1500 rear end w/ RE from a different year or type ?

What is your question?

I have 1990 K1500, 5.7 L, 4WD. , Ext cab/bed, 720R4 trans. Diff. cover has 10 bolts. I'm not sure on the gear ratio. I'd prefer to change out the entire rear end. Do I need an exact match or do I have other options. I understand that gear ratio is specific? Can I find the same ratio on a different year model, or one with a 12 or 14 bolt pattern . What about an upgraded RE if there is such a thing, Are there ways to improve performance, would I want to? For what reason? I just had to have the trans. rebuilt and my diff. goes bad a week later, so cost is an issue. Thanks in advance for any input you can offer!