I have a '73 240z and was wondering what type of oil is good for my manual trans. ?

I have been using Red Line MTF (manual transmission fluid) for quite a few years. I don't know that it's any better than regular 85w-140w but it seems that the transmission does shift a little easier. It is a little more expensive but you only need 1.6 quarts to fill the transmission. I've also been using their lube in the rear as well.