Oil....... What is good to use?

Hi,
Couple questions on oil;

- I have a 3 speed manual trans, what oil should I use? Should it be used with slick50 as well?

- I have and 8 3/4 rear, 741 sure grip, 3:23 gears, what oil should I use and should I add some sort of friction lube for the Posi traction?

Thanks in advance.