98 Astro front differential

I have searched the state and 5 states around for a front diff for my van. It's GT4 and hard to find and expensive. So I stumbled on a 98 Bravada for less than the part I need. Can anybody tell me why I shouldn't use the one out of it? If the gear ratio is different I plan on taking both from the olds. This is my second time at this, my older Astro took a blazer diff.

98 Astro AWD vin W 4.3

Just one option:

http://www.everdrive.com/partdetails.aspx?sku=1523361&utm_source=google&utm_medium=googlebase&utm_campaign=shopping

Thanks lots. So everyone says the GT4 is harder to come by. It seems specific for years 97-98 only. The Bravada I found is 98 and everything looks the same. Bolt places and cv's are identical. I did look at the page you posted abd they need a call for "pricing and availability". It stinks my only free time for research is after hours when everyone is closed for business too.:disappoin