Richard,
Based on Jeff's research, I can't argue that the made in USA version with normal threads was most prevalent on San Jose vehicles. There is ample evidence of that.
However...my perfectly dated pair of fine threaded made in Canada rear shocks throws a wrench into the theory that ALL San Jose shocks were made in USA.
Since the part number lines up perfectly, I can't see why the engine type would have anything to do with it.
Finding more cars with original shocks is not easy, as you know. If we did, we might find a narrow window where Canadian shocks were used on the line.
We did discuss in a previous post the theory that the rear shocks were replaced under warranty. However, to end up with a pair of shocks dated 6L when the car was built in 6M would be moving from one mystery to another.
John