Shifter stop

[FoxHound]

Had the same problem. There is a steel tab that is part of the selector on the shaft that grinds down after 40 years of use. You will need to weld material onto it and grind it to the correct height and shape so that it works properly by restricting selection to reverse from neutral on down. May have to weld/grind a few times to get it just right. This is what I did and my truck shifts just like a brand new one. I don't have any pics of it though, sorry. It's hard to explain but if you look closely you should see where the original tab has worn away.