The soundtrack is now out on CD
After almost 40 years, the soundtrack is finally available.
https://mvdshop.com/products/paul-zaza-carl-zittrer-prom-night-original-1980-motion-picture-soundtrack-cd
Mine came through this morning - it's beautifully presented with some nice liner notes about their approach and writing lyrics that nod to the plot lines.
As well as all music from the film, there six disco tracks that never made the cut and lots of score/incidental music that was also switched or cut.
'Dancin' in the Moonlight' is still THAT bop.