Transmission enquiry....

[Grant Bowker]

In Phil's photo, the (Chev) reverse lockout release lever is on the right.
In David's photo, the (Ford) reverse lockout release lever is on the left.
Both levers are canted forward.
Perhaps someone dismantled their Chev shift tower and then looked at a Ford to see which side the lever should be on (after all, you and I looked at other transmissions for guidance) and because they thought that the lever had to be on the left, put it together incorrectly. (either that or they thought that they had found a magical way to get around the reverse lockout (they might have wanted to this if the mechanism had crudded up and the catch lever broken off short)).
On Phil's truck the lever looks like the longer version, seeming to confirm what the outside truck was showing us, that longer levers seem correct for earlier trucks.
Like all theories, more than one observation is needed for proof.