I have been playing a campaign in feudal Japan for a year now, and I would say that I made great use of the rpg Sengoku, for historical and cultural background, as well as when it came to weapons and armor.
I haven't really bothered about changing the armor tables to fit the specifics of the Japanese samurai (and other warriors) armor.
I have also, of course, made great use of the Martial Arts companion.
Perhaps these might inspire?
http://www.ospreypublishing.com/title_detail.php/title=Q9427~ser=ELI~per=49
http://www.ospreypublishing.com/title_detail.php/title=P5993~ser=ELI~per=49
http://www.ospreypublishing.com/title_detail.php/title=S5732~ser=ELI~per=49
http://www.ospreypublishing.com/title_detail.php/title=P1319~ser=ELI~per=49
http://www.ospreypublishing.com/title_detail.php/title=Q8978~ser=ELI~per=49
www.samurai-archives.com
www.sengoku.com
Just some quick thoughts...
/ninja