I recently heard back from Elvin Cook's partner, and have found a few photos.
Elvin was born 10/10/1929 & passed on 4/1/2008. He & his long time partner, Chris Barrett, were active members of the Mustangs. Chris didn't send any other details. There was no published obituary. I have two photos that I think show him in a nice light.
— Tom Maturo