Interesting info for sure. The hole being too big is just the fact 65-67 used a 1 inch plug and the later years 3/4.
GM must have made the change from the posi tag to the replacement limited slip one in the early 70's. I checked what I have and the oldest NOS one was bought in 76 for a 69 but says limited slip. The trunk decal however says limited slip but the old fluid can says posi.
