1st gen f-body rearend ?

[jonnyc]

i'm getting ready to get the 9" built for my firebird and i can't find my piece of paper that i wrote the dimension from my factory rear.i need to know what the dimension is between the leaf spring perches.i seem to recall that its 42" center/center but just want to confirm.and it should be the same length from each housing end to the center of the spring perch,right?

thanks