are all 12 bolt posi's the same?

[tgh117]

I am wondering if all 12 bolt posi's are the same. My buddy had one rebuilt for his camaro, but went with different axles, so then he had to purchase a new unit. I am now going to replace all the bearings in rear of my truck, and my buddy has offered to give me the posi unit that he had all rebuilt, but I am not sure if this will fit in my truck?

Anybody know the answer?

Thanks in advance.