rear end dimensions

[pac31990]

I need to know a few specific measurements of a stock rear end. I bought a foxbody 8.8 and plan to build it. The measurement for the spring perches are 38.5 inches but where is that measurement taken from. outer edge to outer edge? center to center? I also need to know the same thing for the shock mount and the position of it on the housing tube. Basically i want to have the new rear end mirror the old one as far as mounts and brackets. Thanks in advance.

 

[Locotomb]

https://www.therangerstation.com/stock-ranger-specifications/ford-ranger-rear-axles/