I'm Not a Young Man Anymore only appeared in early 2008 when a bootleg of an April 1967 Velvet Underground performance from The Gymnasium in NYC surfaced. The bootleg also featured the first recorded performance of Sister Ray.
The bootleg has just got an official release as part of the deluxe 3CD - 45th Anniversary "Super Deluxe Edition" of White Light/White Heat
Dean and Britta's version was recorded for 13 Most Beautiful (and titled Not A Young Man Anymore hence turning up where it does in this series). The song was used to soundtrack Lou Reed's coke drinking screen test.
Dean wrote this about the song for an article for Bomb Magazine Scoring Warhol’s Screen Tests
We were a little intimidated at the thought of writing a song to play to Reed’s screen test, perhaps because the Velvets cast a long shadow over the whole Factory scene. We went back and forth between two screen tests of Reed, shot only months apart, both Lou Reed, but seemingly two different people. In the first, early Screen Test, a very young and innocent Reed looks vulnerable, shifting his eyes from side to side. But in the subsequent one, probably shot to project on the Velvets during their Exploding PIastic Inevitable show, Reed has transformed into a rock and roll animal, drinking from a bottle of coca-cola, resplendent in leather jacket and ballorama shades. And when a hitherto unknown Velvets song popped up on the Internet last year—a bootleg of the band performing “I’m Not A Young Man Anymore” live in 1967, shortly after his screen test was filmed—we decided to embrace it.
Here's a live "Screen Tests" performance