There are different cable lengths for different year models, plus different transmission options...
As I dont see an accurate description of what handle or foot mechanism you have installed, all I can offer you is this link to LMC page
http://www.lmctruck.com/icatalog/cb/full.aspx?Page=152
Is this a LWB or SWB?
Handle under dash or foot operated e brake?
Six inches is not much...did you think to pull the cable forward to compress the e brake springs inside the drums?
Or have yo alos added rear discs for a hybrid rear cable length?
We can usually help out, but need this basic info to assist...