Unfortunately there are no modern equivalents of the old school Morley PW's. Morley doesn't currently make anything like it. I believe they have said that the Mark Tremonti Wah was the closest, although still not all that similar. Just get the real deal, they're easy enough to find.
Cliff used an American Big Muff going into a Power Wah Boost (I think it was the Boost at least...).
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