Rear End Info Needed

[Jeffs70]

ok here is what I have a
71 C10 with Trailing arms in the rear and a 12 bolt limited slip rear end.
a 70 with Leaf Rear suspension and a 12 bolt posi rear end.

What I want is the 12 bolt posi in my Trailing arm suspension truck.

I read some things on this and I even asked my brother about doing a swap but that requires that the perches be swapped.

But my main question is are the rear ends the same length and shouldn't everything work properly other then one thing is the posi rear end does not have a place to bolt the pan hard bar. I will just make a bracket to work if possible.