there are OS Giken DOHC heads for both 6 cyl (as mentioned) and 4 cyl L series motors. I think feral eral's site has some pics.

Nissan motorsport department also made a twin cam 4v per cyl head for both 6 (as mentioned) & 4 cyl motors. The 4cyl version was known as a Lz motor.

Some of those Lz twin cam heads made it to Australia on works rally cars 710's in the late 70's to take on the BDA Escorts. These were driven by George Fury and a Scandanavian driver whose name I cannot remember. They were also used on the subsequent works Stanza rally cars. Phill Morriss got hold of one or two of them and was using the Lz head for several years on his awesome 2.4l L20 1600/510 Improved Production car that still holds class records at some tracks more than 12 years later. A few years ago he changed to FJ power, probably for costs and parts availability.

The engine in the 432 is not a weird version of the L series, it is designated 'S20' and is a completely different engine used only in the domestic Japanese market as far as I know.