Another Indy/RHS/X head question

I experienced a 2-3 tenths ET benefit in the 1/4 going from a set of as cast port OEM 360 heads w/1.88/1.60 valves to the as cast port LA-X 1.92/1.625 valve heads. Final chamber cc's were 3-4 less on the LA-X for a bit more compression. Both had similar valve jobs and everything else was the same on the engine and the rest of the car. I don't remember if there were any minor jetting tweaks needed for the change to optimize the heads.