we have only built ONE engine in the last 10 years that used the Vortec heads--he , like you, had read some articles about them---well it takes a spring change(which I seem to remember having to cut for the spring base) different studs, guide plates, etc, and then bigger valves which took some pocket porting, and different intake manifold (think there was issue of drilling tapping for center bolts) and maybe even different headers because the exhaust ports were different---