The heads you have are called peanut port heads. The are good up to about 4000 rpm. Plus they would have to ported and the intake port matched. They are not any good for performance. You would be better off finding a pair of 781s or 049s. They are the best oval port heads for performance. You would like to have 110cc chambers, with KB203 .133 dome would give you 9.781 compression.By the way with the 268H you will need K11-242-3 which is the kit. you can not use the stock springs with that cam.