Dang, that's tempting, but I think those heads would be a little big for my project (400hp 7K rpm 289), lol! I still can't believe the size of the valves on Boss heads, those things must be made to run in the 6500-9000rpm range!
In 1969 the valve size was 2.23/1.71 in a 63cc chamber. Low end torque suffered, so in 1970 they reduced valves to only (!) 2.19/1.71 and 58cc chambers. The Boss 302 was made to twist and high rpm's is where the power is.