need backspacing help on 98 Chevy

My truck is bagged and bodydropped 98 GMC c1500.  I am finally switching the 20s to 22s.. Looking for the right backspacing, width combo.  I have Aim deepdrop a-arms for the front that I am switching out the modified stocker for.  Any help would be great, I know I could measure but its currently torn apart and this has been done a million times before so I know many of you know the perfect combo!!
Thanks!