Trying to get as much sorted out as I possibly can. The old master is a manual master with disc brakes and I'm also going to run manual with disc. So when I took the old master out the pushrod was still on the brake pedal. I unthreaded the pushrod to the brake pedal and put it in the master and measured from the locking nut to the flange.
This measurement was 3.125"
So master cylinder 260-9439 has a pushrod with it attached, and the lock nut threaded as far as it can go makes it about