I am working on my 82 shorty ,I cut the frame behind the cab and did not take a measurement on the rear end location

."Duh"
I am currently installing a 9" w/disc brakes and a triangulated 4 link, all i need is this critical measurement to finish the install.
I have done some research and came up with 117.5" on the wheel base.
Just need some help with that measurement.
randy100unit@yahoo.com