The factory SOHC parts have become ridiculously expensive. Robert Pond makes a nice reproduction of the factory dual plane 2X4 for $2500; that's the one I'd buy if I was after one. I have two originals, and I wouldn't think of letting them go for less than $4K each. Last year on ebay I sold a pair of factory valve covers for $2900! The prices for the factory SOHC parts are way, way up there...