I recently wrote an article for TheHorrorDrunx.com online magazine that sheds a lot of light on the Dr.Phibes series and the proposed sequels. In it are quotes directly from Vincent Price and others.
Also covered in the article are both the Count Yorga and Blacula series.
A great article that needed to be written. I just wish you would have gone into any plan you may know of for how they would have started the third Blacula film. I posted an idea on the Scream Blacula Scream board.
I consider William Marshall and Robert Quarry horror legends in their own right because they really made their vampire characters their own and in the case of Quarry, he starred in the 2 other horror films (Dr. Phibes Rises Again) and (The Zombies of) Sugar Hill. Frankly, after the 3rd or so viewing of the Phibes one, I just noticed what happens to Quarry at the end. It was quite a horror spot.
You have to also remember Quarry had parts in the Horror films THE DEATHMASTER and MADHOUSE at A.I.P. around this time as well.
Get in touch with me on the www.TheHorrorDrunx.com boards and send me a link to that Blacula topic. I'm afraid I don't get over to these boards very often to check back here.