As I recall, "double humps" came with either 1.94 or 2.02 intake valves. Not sure about the exhausts, but I think the 1.94s had 1.50 exhaust and the 2.02s had 1.60s.
I think the heads with smaller valves would work on a 283...wasn't that what was used on the 57 "fuelie?"
If I'm mistaken, I'm sure someone will correct me.
