Hi Connie, thanks for this link! It was fun to read David's words about Grayson, Thayer, and of course, Johnny!
I do wish they would get someone to correct all the typos on that site, but you can't have it all, can you?
As I recall it, there's a slightly truncated version of the 1968 Ron Barry interview with Jonathan, Grayson, Humbert, Don Briscoe, Robert Rodan, and the unflappable Roger Davis (urghhh), on the Varese Sarabande reissue of the original Dark Shadows soundtrack album (the one from 1969). They had a lot of room on that CD because the original LP was so short.
Unfortunately, the Thayer David Ron Barry interview has yet to be issued on CD, but a fan was kind enough to send me a tape of it, and I think Bobubas sells it, too.
Best, G.