There was a B5 blue 70 cuda that was wrecked with less than 10k miles on it that sat for a very long time outside a business a few towns up US 30. Hit in the back very hard. Bent the frame rails, shoved it all ahead, not pretty. I looked at it a couple of times as it had a dana under it. The guy where it set claimed it was a 383 727 ordered with the drag pak 4.10. It was a column shift, no frills piece. Claimed the guy bought it as a budget street brawler, and was real fast while it lasted. I did not see the fender tag.
I did go check my 70 challenger book though, and you are right in that it doesn't show it being offered for a 383.

Is it possible it was a special order?