Those are a much later casting than the W2 heads I sold earlier this year. The set I had were part number 3870812 and casting number 3870810. Mine were an open chamber race head. Yours appear to be a closed chamber race head or else the heads have been milled so much that they turned an open chamber into a closed chamber. The set I had was very early production and didn't have the ribs. I also had an early 340 block. Sold it as a package deal to a guy who always wanted a W2 340 combo for his Duster. Ended up making about 600 hp on the dyno. Should be a fun street combo.