Diamond Heads: http://www.shadydellspeedshop.com/diamondheads.htm

They're from the Early 80's ~1981-1982ish

The rectangle port version are very similar to an INDY head. It was just a modified W2 cast in aluminum. Bigger exhaust port & much less restrictive water jackets around intake bowls & no water jacket under the short turn so you could make the intake ports as big as your heart desired. Also have little wider valve spacing than a W2, sort of like an INDY for use with larger valves.... They were VERY $ back in the day & very few sets were cast, I was told around 50-75 sets of the version Scott has by an old timer who still works at Diamond. These heads were what Ritter/Weber started out with in their Comp Eliminator program & evolved into Arrington heads. Arrington was also involved in having Diamond cast these heads for circle track use..... They were used in ARCA in the 80's & carry a Direct Connection casting/part #.

Make about same power as a rectangle INDY head.... 18* valve angle. Little soft on the castings & Ritter/Weber had problems blowing the corners off of them on their engines, but they were running 17:1. Use W2 rocker gear.....