Reverse detent on a type E 4 speed gearbox.

I own a 1979 Escort mk2 two door race car with a type E 4 speed single rail gearbox. The reverse detent is virtually non existant, & I constantly can't find second gear when changing from third back to second, resulting in compression lock-up when I do eventually find it. Not good in a corner. I have changed the saddle between the selector fork & shift rail, but no change. Additionally, as I don't have to depress the gearlever to get reverse, I often get reverse when trying to select first.
My question to you learned ones is:- is the reverse detent a function of the gearlever, or is it in the gearbox itself ?