T Spring on 39 banjo

Getting set to put the perches on my diff, but I am reading conflicting information about how far the perches should be set apart. Has anyone who's done this got the measurement handy?
It's going into an A chassis.

 

Never mind. 48.5" if anyone else is doing it. Should be enough room for the brake fittings, and I think the shackle preload came out pretty good.

 

Now that's a handsome lookin setup!