A couple years ago at SEMA, we got to inspect (and drool over) the OS Giken twin-cam TC-24, an incredibly-rare (and pricey) piece of history...
Here's video of a sweet-sounding Datsun 1600 fitted with an OS GIKEN twin-cam head.
[youtube]http://www.youtube.com/watch?v=tFIk8EbHK28[/youtube]