It is uncommon and you could call it "rare".
Dictionary definition: Rare: Infrequently occurring; uncommon
I have one and I got it because it is an oddity and it is the first automatic transmission used in a Chevrolet truck (non-military GMC trucks used it in 1952/53).
What does "rare" mean to you? Your truck as equipped is uncommon and thus it is rare. However, it is not quite as rare as hen's teeth.
Have you driven your truck? Does it shift nicely?
