I didn't want to detract from Derek's massive thread but I was curious if there was any information around on this video:
http://tominis.info/watch/hDCfZUIMom8/dohc-twin-cam-l28-datsun-z-car.html
Seems he mated 3 different KA24DE heads to make this happen.
Video is marked for 8 years ago, so I'm wondering if the guy was on here before or if anyone knows any other info on this thing. Looks interesting to say the least, but I haven't found anything else on it.