Hi Will,
Welcome to this site.
I did a write-up some years back on the differences between the '69 B/B P/S pumps. You are correct, 1969 is a one year only for this style pump.
Camaro, Chevelle, and Nova share the same P/S pump can, with the location of the return line tube. There are some internal differences between variable and non-variable.
The Impala or Pass car pump has a different return line direction. Points away from the engine.
Here is the link, hope you find it usefull.
- Warren
https://www.yenko.net/forum/showthread.php?t=127049