Here's another interview from around the same time in ~1979, where he says he has signed up to do the Conan movie, so it's probably around 6 months earlier than the Carson interview. (Or however long it takes his hair to get that long, from the length it is here ...)
LOOKS UNTRAINED ...he really got himself good enough in conan,some scenes he looks smallish ,soft and others pretty pumped and fuller .interesting stuff,he really stopped for some time and got normal ,probably other than the heart operation is still going strong into 60/70's unlike most heavy steroid users,lets face it he took enough..