If it’s what I think you’re talking about, you’re somewhat correct. I just completely rebuilt the column on my 66 Belvedere. On the shifter handle, the part that slides into the ‘hump’ on the collar, you’ll see a small indent where the spring goes. You have to collapse the spring slightly as you slide the handle into that hump. Then the retaining pin goes into the hump and through the aligning hole in the handle and out the other side of the hump.
Not sure if I’m describing the parts properly but I can provide a few photos.
On the hump on my collar the holes where slightly elongated causing the handle to move slightly while shifting gears. I took a small amount of JB Weld and put it in the holes. After it cured I redrilled the hole and tapped in the retainer pin. Painted the column and it looks and work like new. Unfortunately I don’t know if the spring or pin are available. Maybe someone here has converted to a floor shift and has the parts. Let me know if you have any other questions.
