is it common on a 1985 k5 blazer for the frame to break right behind the steering box? i was told it cracked there but didnt bust off

 

This is a very common problem on full size blazers. Especially when running bigger tires and turning when offroad in the ruts and against rocks etc. There are several kits available to address this problem. Here is one of them... http://www.autofab.com/sbgk%20100.htm

 

Yep. Very common. I was actually surprised to find my frame in good condition without cracks! There are many, many kits that can either be bolted in or welded in. I will be putting the weld in kit on mine just for safety.