If your not the original owner, don't be surprised if the reverse brake cone has a broken tab. Many liked to ram it into 1st from reverse or 1st to reverse. The 2 brass blockers on the 5th gear may be badly worn as may the dog teeth on 5th and 1/2 slider. ( only 1 blocker in a standard rebuild kit)
I rebuilt one back in march and above was obvious. Previous owner said there was no 5th, I found the tab broken on the reverse cone, snap ring off the 5th driven and 5th driven moved off the splines on the main shaft. Yah, there was no 5th alright.